I’ll admit that the reading I’ve done on white-nose syndrome over the last few weeks has been pretty depressing- at one point I saw an estimate of 6.7 million bat deaths so far (Cohn 2012), which is a horrifying number. But I think it would be even more horrifying to simply resign ourselves to the catastrophe which seems to be at hand. We may not fully understand how the fungus works or how to stop it, but we can work to slow its progress and support bat populations in infected areas and elsewhere.
Want some ideas on how to help?
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Learn more about the actors
Looking for more details?
- The USFWS has set up a website devoted to white-nose syndrome, including directions on how to keep human visitors to caves from becoming transportation for fungal spores (including rubber caving boots).
- If you are thinking of adding bat boxes to your house or property, Bat Conservation International has design recommendations and tips for attracting bats. Even though the bats may not spend the winter in your boxes, you can give them easy access to high quality habitat during the summer which hopefully leads to a better chance of making it through the winter.
You can also contribute to bat research:
- It’s almost the end of this year’s season, but you can still contribute to the Pennsylvania yearly bat count if you complete a simple count by the end of the month (or you can get a head start planning for next year!).
- Maine Audubon would like to hear from you if you know the location of roosting colonies.
And remember that good press for bats is helpful, too!
- Bat Conservation International is looking for volunteers to be docents and educators in Austin and New Braunfels, Texas.
Works cited:
Cohn, JP. 2012. Bats and white-nose syndrome still a conundrum. BioScience 62: 444.
Looking through the most recent literature on white-nose syndrome isn’t exactly reassuring, although it does suggest that progress is being made in understanding how the fungus affects bats and what conditions may help bats survive infection. As of last year, at least 19 US states and 4 Canadian provinces contained infected bats (Blehert 2012) and three additional species had been infected: gray bat, southeastern bat, and cave bat (Foley et al. 2011).
“Bat survey in Ohio”- because these little brown bats roost in such large numbers, the chance of passing along infection is high.
Little brown bats continue to be particularly hard hit, and we are developing a better picture of how and why the fungus is so devastating for that species. It has been suggested, based on studies of both bats and ground squirrels, that dehydration is the trigger for awakening during hibernation (Willis et al. 2011), and wings are critical moderators of water loss in bats. Wings damaged by the fungus may lead to greater water loss and therefore more time spent out of torpor during the winter. Little brown bats do exhibit more evaporative water loss than other species, which could be why they are so susceptible to the fungus. And some behaviors of the bats themselves may lead to infection and mortality. Prior to hibernation, little brown bats swarm and breed, so individuals carrying the fungal spores have the opportunity to infect others (Hallam & Federico 2012). This could be a particular issue for males who spend the summer using colder roosts and may therefore harbor the fungus between winters (see below for more on the temperature problem). It is also possible that males are more likely to succumb to white-nose syndrome: the torpor optimization hypothesis states that individuals with greater energy reserves should reduce their time in torpor (so that they are less vulnerable to predation and other threats) unless those energy reserves are vital to spring survival or reproduction (Jonasson & Willis 2011)- since female little brown bats need extra energy for springtime pregnancy, they spend more of the winter in torpor and should therefore have more reserves in late winter when white-nose syndrome is most prevalent. Females should have a better chance of surviving infection. Surviving the winter may not be enough, though. Infected females with the energy to survive to spring may not have enough energy to reproduce, so individuals that did not survive can’t be replaced by a new generation. And since males may be particularly susceptible, this could lead to massive imbalances in the sex ratio of colonies, with a variety of consequences including decreased genetic diversity and lower reproductive success.
Is there any way to counteract the fungus? Possibly, although there are still quite a few unanswered questions about this. Laboratory investigation of G. destructans suggests that optimal growth occurs between 12.5 and 15.8 °C and no growth takes place in temperatures above 19.8 °C (Verant et al. 2012)- it could be possible that colder temperatures in hibernacula would slow the development of the fungus, and it may also be possible that bats which experience warmer temperatures during the summer may be able to rid themselves of infections (which is why male little brown bats in colder summer roosts could harbor the fungus). On the other side of the temperature issue, since surviving the winter is so energy-dependent, some researchers have suggested that, if infected bats had access to warmer areas when they woke up from torpor, they might be able to conserve energy and have a better chance of surviving the winter (Boyles & Willis 2010)- however, general warming of hibernacula would increase the rate of water loss for the colony, plus it would be complicated to create artificially warmer sections of a cave, so this idea is tricky. Certainly the question is how to make sure that infected bats have enough energy to survive the winter- and comparison of mortality of bats across the Northeast and in Europe suggests that longer winters spent in drier hibernacula lead to more bat deaths (Puechmaille et al. 2011; Flory et al. 2012), so increasing cave humidity in some areas could be helpful. Boyles & Willis (2010) felt that making food available in caves for bats that came out of torpor might be helpful, but wasn’t a practical solution. Hallam & Federico (2012) suggested that a boost in energy reserves right before hibernation might be the key and advocated planting vegetation near hibernacula that would attract foraging moths to give the bats a little help at the end of the summer.
To a certain extent, scientists are still trying to determine exactly what the fungus is doing to bats as it develops through the winter, but, given how quickly it has spread and how devastating it has been to some species, there isn’t really an opportunity to sit back and wait for lots of data before putting a response plan in place. Bats need help now, and not just from scientists trying to understand the energetics of the infection- we all have a part to play, whether that’s in prevention or support or recovery. For my final post of the month, I’ll look at the ways that we can get involved in bat conservation in the face of white-nose syndrome.
Works cited:
Blehert, DS. 2012. Fungal disease and the developing story of bat white-nose syndrome. PLoS Pathogens 8(7): e1002779.
Boyles, JG and CKR Willis. 2010. Could localized warm areas inside cold caves reduce mortality of hibernating bats affected by white-nose syndrome? Frontiers in Ecology and the Environment 8: 92-98.
Foley, J, Clifford, D, Castle, K, Cryan, P, and RS Ostfeld. 2012. Investigating and managing the rapid emergence of white-nose syndrome, a novel, fatal, infectious disease of hibernating bats. Conservation Biology 25: 223-231.
Flory, AR, Kumar, S, Stohlgren, TJ, and PM Cryan. 2012. Environmental conditions associated with bat white-nose syndrome mortality in the north-eastern United States. Journal of Applied Ecology 49: 680-689.
Hallam, TG and P Federico. 2012. The panzootic white-nose syndrome: an environmentally constrained disease? Transboundary and Emerging Diseases 59: 269-278.
Jonasson, KA and CKR Willis. 2011. Changes in body condition of hibernating bats supports the thrifty female hypothesis and predict consequences for populations with white-nose syndrome. PLoS ONE 6(6): e21061.
Puechmaille, SJ, Wibbelt, G, Korn, V, Fuller, H, Forget, F, et al. 2011. Pan-European distribution of white-nose syndrome fungus (Geomyces destructans) not associated with mass mortality. PLoS ONE 6(4): e19167.
Verant, ML, Boyles, JG, Waldrep Jr, W, Wibbelt, G, and DS Blehert. 2012. Temperature-dependent growth of Geomyces destructans, the fungus that causes bat white-nose syndrome. PLoS ONE 7(9): e46280.
Willis, CKR, Menzies, AK, Boyles, JG, and MS Wojciechowski. 2011. Evaporative water loss is a plausible explanation for mortality of bats from white-nose syndrome. Integrative and Comparative Biology 51: 364-373.
Over the past week, I’ve been looking into when and how scientists first became aware of white-nose syndrome in northeast bats, as well as what the loss of those bats could mean for all of us. It’s pretty depressing reading on the whole- especially when you realize that it has developed so quickly.
When bats fly into the strings of the harp trap, they fall into the bag below and can be examined by researchers.
What were the first hints that something was wrong? I’m quite sure of the how and where, but the when on this one seems to be unresolved- according to the USDA in February 2006 (or during the winter of 2006/2007 according to US Fish & Wildlife, or in February 2007 according to a 2008 article in BioScience [Cohn 2008]), dead and dying bats were found in a cave near Albany, NY. Some affected bats featured white fungal spores on their faces which both suggested some type of infection and gave the disease its name. By 2010, the problem had spread more than 1300 km and infected caves had been found throughout much of the Northeast and into Canada (Wibbelt et al. 2010). I saw a range of estimates for mortality- one suggested that over 1 million bats had died by 2010 (Cryan et al. 2010); another that losses at individual hibernacula topped 75% (Bolyes & Willis 2010); and a third reported that at a mine in Vermont where scientists had previously captured 900 bats, only one had been captured in 2009 ( really?! That’s terrifying! [Burton 2009]). 6 species of bats which hibernate are impacted in North America: big brown bat, eastern small-footed bat, little brown bat, northern long-eared bat, tricolored bat, and Indiana bat. Of these, the little brown bat has seen the greatest losses (I saw one prediction that, if the average mortality rate of the first three years continued, the little brown bat could be regionally extinct within 16 years- Frick et al. 2010), and the Indiana bat is also of great concern because it is endangered.
Checking wings for signs of damage.
What is happening to the bats? Researchers have isolated and identified the fungus producing the white spores- Geomyces destructans prefers cold conditions and does not grow when temperatures are above 68° F/ 20° C. Although the white muzzle of affected bats is a very obvious sign of infection, the fungus itself grows over other parts of the body as well. The wings are a particular target for the fungus because they are large areas of exposed membrane, and the fungus actually grows into the bat (which seems quite creepy to me- some researchers think that the fungus can do this because the bat’s immune system, like the bat, is hibernating) (Cryan et al. 2010). So is this a new disease? It doesn’t appear that way, although there are questions about why things are happening the way they are now. Scientists in Europe have found the same fungus on at least 5 species of bat, but without the high rate of mortality and have even found some infected bats that recovered (Wibbelt et al. 2010). G. destructans seems to be highly lethal to bats in North America, but not to bats in Europe. How does the fungus kill bats? There are still questions about exactly which characteristics of the dead and dying bats are directly caused by the fungus and which are indirect, but there are some clear patterns and hypotheses. Infected bats appear to rouse from hibernation more often, so they use up their energy reserves more quickly (it can take up to 400 times more energy to be awake in the hibernacula than to be in torpor! [Boyles & Willis 2010]). Because they are running out of energy reserves earlier in the year, there is no food available if they attempt to forage. Some have suggested that the bats are waking up more frequently because of the discomfort of fungus growing into their wings (Cryan et al. 2010). In addition, the wings are damaged by the fungus which has several implications: first, wings are important for regulating temperature and water-loss, and second, even if the bat survives to spring, its foraging is impaired.
Why should this matter to us? Although bats haven’t always been popular animals, they are pretty important to how an ecosystem functions and help us in several ways. In the case of the bats being decimated by white-nose syndrome, these are all insect eaters. A single little brown bat eats 4-8g of insects each night (Boyles & Willis 2010), and a colony of 150 big brown bats eats an estimated 1.3 million insects in a year (Boyles et al. 2011). If we lose the bats, think of how many more insects will bother both us and the crops we grow. Boyles et al. (2011) estimated that bats within North America prevent $3.7 million in agricultural losses each year. Although dealing with a different bat in the US, Cleveland et al. (2006) suggested that consumption of bollworm moths by Brazilian free-tailed bats in Texas allowed cotton farmers to avoid one or two pesticide applications- that seems like a win-win situation: fewer insect pests, fewer chemicals in the environment, less work for farmers, happy bats.
So bats in North America play a big role in regulating insect pests, and those in the Northeast, especially, are in big trouble. There are still some questions about exactly how white-nose syndrome operates and spreads, but researchers have already started looking in how best to combat it and support bat populations. For my next post, I’ll review some of the latest information we have, as well as suggestions that have been made to help bats in trouble.
Works cited:
Boyles, JG, Cryan, PM, McCracken, GF, and TH Kunz. 2011. Economic importance of bats in agriculture. Science 332: 41-42.
Boyles, JG and CKR Willis. 2010. Could localized warm areas inside cold caves reduce mortality of hibernating bats affected by white-nose syndrome? Frontiers in Ecology and the Environment 8: 92-98.
Burton, Adrian. 2009. White-nose syndrome plan in the pipeline. Frontiers in Ecology and the Environment 7: 459.
Cleveland, CJ, Betke, M, Federico, P, Frank, JD, Hallam, TG, Horn, J, Lopez, Jr, JD, McCracken, GF, Medellin, RA, Moreno-Valdez, A, Sansone, CG, Westbrook, JK, and TH Kunz. 2006. Economic value of the pest control service provided by Brazilian free-tailed bats in south-central Texas. Frontiers in Ecology and the Environment 4: 238-243.
Cohn, JP. 2008. White-nose syndrome threatens bats. BioScience 58: 1098.
Cryan, PM, Meteyer, CU, Boyles, JG, and DS Blehert. 2010. Wing pathology of white-nose syndrome in bats suggest life-threatening disruption of physiology. BMC Biology 8: 135.
Frick, WF, Pollock, JF, Hicks, AC, Langwig, KE, Reynolds, DS, Turner, CG, Butchkoski, CM, and TH Kunz. 2010. An emerging disease causes regional population collapse of a common North American bat species. Science 329: 679- 682.
Wibbelt, G, Kurth, A, Hellmann, D, Weishaar, M, Barlow, A, Veith, M, Pruger, J, Gorfol, T, Grosche, L, Bontadina, F, Zophel, U, Seidl, H-P, Cryan, PM, and DS Blehert. 2010. White-nose syndrome fungus (Geomyces destructans) in bats, Europe. Emerging Infectious Diseases 16: 1237-1243.
This month I had some help picking a topic to focus on- a fellow doctoral student at the University of Louisiana at Lafayette had approached me about doing something together and then suggested bats as a topic. To be specific, she suggested white-nose syndrome, and I agreed with her for several reasons: first, bats are sometimes seen as scary or dangerous, so it’s good to look at how they fit into ecosystems and even benefit us; second, bat conservation is a pretty large issue, so being able to narrow down a bit is helpful when it comes time to gather information; and third, white-nose syndrome is a big problem for cave-dwelling bats in the Northeast, especially, and, even as it spreads from population to population, researchers are still trying to figure out how best to stop it.
A bat we captured in Louisiana- photo by Jessica Schultz
My knowledge of white-nose syndrome, or bats in general, is pretty limited. I have a little experience with capturing bats both in the US and elsewhere for research, and I did have the opportunity to care for a few injured bats while I was in Texas, although typically we would stabilize the animals and then transfer them to a bat-specific facility (I have to say they were pretty relaxed customers- very few wild animals are as willing to be hand-fed). I have also seen bats flying at dusk from time to time (or, in my personal favorite memory, hitting the hat of my brother as he sat fishing off the back of the boat and nearly scaring him into the water). They seem like remarkable and fragile creatures- I find their aerobatics pretty amazing (some were so adept at getting around or through the strings of the harp trap!) and I love the fact that some species live in massive colonies. I know that some bats are very good at eating insects, particularly swarming ones (like gnats), so I definitely appreciate their help in keeping the bugs away.
What I know about white-nose syndrome is as follows: researchers started noticing higher mortality for bats coming out of hibernation with whitish fungus on their faces; it seemed to be passed from bat to bat while roosting together in caves; and it seemed to be spreading from cave to cave in the Northeast. Bats that are afflicted with white-nose syndrome seem to come out of hibernation earlier and use up their stored energy before enough spring food becomes available, although maybe the order is the other way around. Although this fungus exists in Europe as well, it does not appear to be causing the same issues over there, so North American bats are at the greatest risk.
This month my goal is to get a better sense of how white-nose syndrome is impacting bat populations, how it is being spread, and the ways in which we can combat it. I’d also like to support a balanced view of the role bats play in the environment- I’m sure they could use a little good press. And I’m very excited to be collaborating with others to present some of this information- hopefully we can put together something that is both informative and engaging. So it should be a pretty interesting month- stick with us as we investigate white-nose syndrome and the ways we can support bat populations.
Over the past few weeks I’ve been looking into conservation issues involving parrots, and it turns out that there are two very different sides to this story: on the one hand, habitat destruction and the pet trade are threatening wild populations around the world; on the other hand, the pet trade (and to a certain extent habitat modification) has led to the release of parrots in new locations where some invasive populations have been able to establish. Addressing these issues is complicated, in part because poaching and smuggling is involved, and also because populations founded by released animals have a lot of supporters who don’t want the birds to be treated as invasives. So how do we make sure that wild populations don’t disappear from their native ranges and try to slow the spread of non-native species? There are many ways that we can contribute to these efforts, so I think there is something for everyone here.
Blue macaws!
For the parrot and parakeet fancier:
- Hopefully it goes without saying, but never release a pet bird into the wild, and there are many good reasons for this aside from the invasive species aspect- many birds, including parrots, must learn how to be effective foragers and evaders of predators- if they don’t have those skills and are released to have a ‘normal, wild life’, they oftentimes starve or are easy prey.
- When purchasing a bird, ensure that it is captive-reared and has the paperwork to prove it (if it was bred and raised in your own country, even better)- this will reduce pressure on wild populations from the pet trade and hopefully cut down on the black market as well.
Around the house:
- Plant more native species- we often don’t think about how many of the plants in our gardens are exotics, but there are concerns about seeds and fruit from these being spread. In addition, these plants can provide an extra food base for exotic animals, such as parrots, and support population expansion. (And let me point out here that the goal is to not to deprive invasive parrot species of all food- but parrot populations with a smaller food base will be in breeding condition less often, leading to fewer chicks, and slower population growth.)
- Buy bird-friendly coffee- the Smithsonian Migratory Bird Center has a certification program to ensure that migratory and tropical birds (such as parrots) are not negatively impacted by coffee production.
- Be sure to recycle paper products and buy recycled paper to help reduce logging pressure on remaining parrot habitat.
Farther afield:
- If you live near the Phoenix Zoo, which hosts a thick-billed parrot captive breeding program, collect and donate pine cones- it takes a lot of seeds to feed those birds, and they are happy to have your help for the parrot food supply. (And my guess is that other zoos probably have similar programs, so, if you’re not near Phoenix, talk to your local zoo about what you can do to help parrots.)
- If you are in New South Wales, Australia, help Conservation Volunteers plant food trees and construct artificial nests for Australia’s superb parrot.
- Do you have translation, web design, or data entry skills? The World Parrot Trust has a wishlist for donations in-kind, including services, so here’s your chance to get involved without having to get dirty.
- A number of organizations have Adopt-A-Nest programs, including Bird Endowment which works with blue macaws in Bolivia.
- Looking for a real challenge? You can volunteer in the field with ProFauna Indonesia– help with education, parrot surveys, and a variety of other tasks.
The ideas above run the gamut in terms of cost and time commitment, and I’ve only scratched the surface- find what works for you and go to it- I’d love to hear about how your adventures!
In my last post, I looked at the status of several wild parrot species which have been negatively impacted by habitat loss, hunting, and other human activities. This week in my reading I investigated the other side of the equation: invasive parrot populations around the world. To be perfectly honest, although I had been vaguely aware of this issue in the US, I had no idea about the true extent of their presence outside of their native ranges. Or how complicated the status of invasive parrot species could be- yellow-crested cockatoos, for example, are considered Critically Endangered by the IUCN, but are a non-native species in Singapore where they exploit exotic plants and native seeds and fruits, potentially reducing the supply for native birds and possibly lowering plant recruitment by grinding seeds and eating immature fruit (Neo 2012)- so is it a good thing or a bad thing that they have established a population in the city?
“Brooklyn Parrots”- monk parakeets living in the temperate zone
Another complication has been determining whether or not a population has become established and is reproducing. Parrots are long-lived animals and do not have frequent or large clutches, so it can be difficult to figure out if the parrots you see in the same place year after year are new birds from a stable, reproducing population or are the same birds simply living out their long lives (Runde et al. 2007). This appears to be partially dependent on whether the birds were captive-reared or wild-caught (Carrete & Tella 2008)- wild-caught birds who then escape from their confinement or are released are more likely to survive in the wild because they retain the skills needed (such as predator avoidance), while captive-reared birds have often lost those responses. It sometimes turns out that what had seemed like a stable or growing population could not really survive in the wild (budgies intentionally released in the Isles of Scilly, UK formed a growing population for 6 years, and then rapidly disappeared once the person feeding them moved away [Butler 2005]), while other populations which seem like they shouldn’t be able to persist do so (witness tropical monk parakeets living through Illinois winters [Goncalves da Silva et al. 2010]).
So what type of scale are we talking about with parrot invasions? It’s pretty impressive, to be honest, and we can largely take the credit for making certain species global personalities. Ring-necked parakeets (also referred to in some literature as rose-ringed parakeets, which was a bit confusing at first) hail from Asia and Africa and are now considered by some to have the largest global distribution of any parrot species (Shwartz et al. 2009) having added at least 35 new countries to their range. Monk parakeets are originally from southern South America, but can now be found throughout the Caribbean, North America, Europe, Japan, and elsewhere (Goncalves da Silva et al. 2010). In 2005, the American Ornithologists’ Union listed 7 parrot species as established in the US (Butler 2005) and there was the possibility of 5 more being added. Where are these birds coming from? The pet-trade, for the most part- whether they are escapees or intentional releases, these species were initially imported into various countries to be kept as pets. Carrete and Tella (2008) estimated that 5-10 million birds (not just parrots) are captured annually for the pet trade. The US had been the largest importer of monk parakeets and other species (64,225 monk parakeets between 1968 and 1972! [Russello et al. 2008]), and, although the Wild Bird Conservation Act of 1992 plus bans on specific species have changed that, Runde et al. (2007) estimated that around 17,000 parrots are still imported annually. Genetic studies by a number of these researchers indicates that many non-native populations come from pet-trade stock.
Ring-necked parakeets, now an established population in the UK. Image from the GB non-native species secretariat, under Crown copyright.
Are they really causing problems in their new locations? In some respects, that depends on your point of view, but there are (I think) legitimate issues that have to be addressed. For the same reasons that parrots are popular as pets, they tend to have a lot of supporters when they exist in non-native populations- people enjoy watching them and in some cases have been quite protective about these new populations. In a Barcelona survey, 80% of respondents were against control of invasive monk parakeets in the city (Senar & Domenech 2001). Many parrots, however, are cavity nesters and may compete with native species in areas where nesting sites are limited (which is a common situation, by the way, in areas of the developed world because of intensive forest management) (Strubbe & Matthysen 2007). Strubbe and Matthysen (2007) found a negative correlation between parakeet and nuthatch presence- because ring-necked parakeets begin breeding considerably earlier than native nuthatches, they may monopolize breeding sites in the areas where the two species overlap. A similar concern for the echo parakeet in Mauritius (whose status I mentioned last week) led to programs to remove invasive ring-necked parakeets from nesting cavities that could be used by the echo parakeet (Strubbe et al. 2010). As I mentioned above, parrots also consume immature fruit, and seeds passing through the digestive system tend not to be viable- this can lead to changes in habitat plant composition (Neo 2012). And there are impacts that you might not have expected. Monk parakeets do not use cavities, but instead construct their own nests which can be pretty elaborate affairs- to do this, they use a variety of branches, some of which are snapped off of trees, leading to tree damage (Conroy & Senar 2009). Because these nests get very big and are usually high off the ground, they pose a danger to anything underneath in windy conditions, and it turns out that monk parakeets like to use metal structures from power grids for support- in 2001, over 1000 electrical outages caused by monk parakeet nests cost around $585,000 in south Florida (Russello et al. 2008). With expanding parakeet populations and ranges, think about what that means for our power grid.
So parrots are both in peril and invasive species, which I think, although complicated, is helpful for reminding us that very rarely are environmental situations completely black and white- the global environment is a pretty complicated web and human beings play a very active part in many aspects of that. Because we are involved in so much of how the environment changes, we also have many opportunities to direct or mitigate that change, so for my next post, I’ll look into how we can both support parrot conservation and slow the spread of invasive populations.
Works cited:
Butler, CJ. 2005. Feral parrots in the continental United States and United Kingdom: past, present, and future. Journal of Avian Medicine and Surgery 19: 142-149.
Carrete, M and JL Tella. 2008. Wild-bird trade and exotic invasions: a new link of conservation concern? Frontiers in Ecology and the Environment 6: 207-211.
Conroy, MJ and JC Senar. 2009. Integration of demographic analyses and decision modeling in support of management of invasive monk parakeets, an urban and agricultural pest. In DL Thomson et al. eds. Modeling Demographic Processes in Marked Populations, Environmental and Ecological Statistics 3: Springer US.
Goncalves da Silva, A, Eberhard, JR, Wright, TF, Avery, ML, and MA Russello. 2010. Genetic evidence for high propagule pressure and long-distance dispersal in monk parakeet (Myiopsitta monachus) invasive populations. Molecular Ecology 19: 3336-3350.
Neo, ML. 2012. A review of three alien parrots in Singapore. Nature in Singapore 5: 241-248.
Runde, DE, Pitt, WC, and JT Foster. 2007. Population ecology and some potential impacts of emerging populations of exotic parrots. Managing Vertebrate Invasive Species: Paper 42.
Russello, MA, Avery, ML, and TF Wright. 2008. Genetic evidence links invasive monk parakeet populations in the United States to the international pet trade. BMC Evolutionary Biology 8: 217.
Senar, JC and J Domenech. 2001. Volaracio dels danys per Cotorra de pit gris al Baix Llobregat I a la ciutat de Barcelona. Museu de Ciencies Naturals, Barcelona.
Shwartz, A, Strubbe, D, Butler, CJ, Matthysen, E, and S Kark. 2009. The effect of enemy-release and climate conditions on invasive birds: a regional test using the rose-ringed parakeet (Psittacula krameri) as a case study. Diversity and Distributions 15:310-318.
Strubbe, D and E Matthysen. 2007. Invasive ring-necked parakeets Psittacula krameri in Belgium: habitat selection and impact on native birds. Ecography 30: 578-588.
Strubbe, D, Matthysen, E, and CH Graham. 2010. Assessing the potential impact of invasive ring-necked parakeets Psittacula krameri on native nuthatches Sitta europeae in Belgium. Journal of Applied Ecology 47: 549-557.
Over the past week, I’ve looked into aspects of parrot conservation, and there seemed to be something of a split between two lines of investigation: parrots threatened in their native range, and parrots causing problems as introduced species. This week I’ll concentrate on the former and then next week, I’ll gather some information on the invasive species issue. As charismatic, intelligent animals, parrots have caught the eye and interest of humans for quite some time, but the emphasis there seems to have been on how having pet parrots and parrot feathers could improve our happiness- we weren’t paying as much attention to the needs of wild populations. Thanks largely to habitat loss and hunting (for live and dead animals), of the 355 living species of parrot, 96 were at high risk of extinction in their native range by 2011 (Legault et al. 2011)- that’s more than 25% of extant species and doesn’t count those already lost. In the Americas by 2001 46 of 145 species were at risk (Milius 2001).
A Moluccan cockatoo who is quite happy to be out of his personal cage
Dwindling wild populations have become more vulnerable to a variety of events. The wild Puerto Rican parrot population, for example, had been reduced to 13 individuals in one location in 1975 (Beissinger et al. 2008)- a huge hurricane hitting in exactly the right (or wrong) spot, a freak fire, a disease outbreak- any of those things could have wiped out the remaining birds. And there are long-term consequences when a population gest that small- inbreeding depression caused by lack of genetic variation can leave animals susceptible to changes in their environment and with decreased reproductive success. 30 years after that low, the Puerto Rican parrot numbered only 30-35 individuals (White et al. 2005), which is an unusually slow rate of growth. When shrinking habitat is added to the equation, recovery can be really challenging. One of the concerns about the two species of parrot found on the island of Dominica is that they will start competing with each other as more and more land is developed for other uses (Christian et al. 1994), and so the question is how to support both populations right now plus protect habitat for the future. In New Zealand, the wild population of orange-fronted parakeets had fallen to about 300 by 2009, partly because of habitat loss, but also due to predation by introduced species such as house cats and rats (Ortiz-Catedral and Brunton 2009b), so conservation planners had to investigate whether some habitats were safer than others for population recovery. Are these smaller populations doomed? Not necessarily- the wild echo parakeet population on Mauritius was down to 8-12 animals in the mid-1980s (Taylor and Parkin 2010), but has been able to rebound to almost 600 in 2012- in fact, starting in 2007, it’s conservation status was down-graded from critically endangered to endangered. Obviously, it’s not out of the woods yet, but it’s definitely a cause for hope.
What can be done to help these smaller populations? From the literature, it appears to boil down to three main things: habitat restoration, reintroduction, and education. As Legault et al. (2011) remarked, most parrots need forests, so habitat conversion is a real problem for these animals. Dominica has worked to create parks that encompass some of the parrots’ range, as well as supporting public education and the development of ecotourism as a means of slowing further habitat loss (Christian et al. 1994; Christian et al. 1996). Researchers in New Zealand have used several predator-free small islands as release sites for endangered parakeet species- this way more habitat is available to the species, and the released populations can acclimate and expand in a safer environment (Ortiz-Catedral and Brunton 2009a; Ortiz-Catedral and Brunton 2009b). (And remember that many reintroduced birds are captive-reared- they don’t always know how to behave around predators- the releases of thick-billed parrots in Arizona recounted in Snyder et al. (1994) are particularly depressing in that respect.) There are now 2 Puerto Rican parrot populations in the wild after a series of releases established a new group in a different part of the island- this will (hopefully) increase genetic variability, but also serves as a buffer in case a natural disaster hits the original group (iucnredlist.org).
So things are not entirely rosy when we look at native parrot populations around the world, but that’s only one side of the story- for next week I’ll look at the other end of the spectrum in those places where parrots are new, and not always wanted, arrivals.
Works cited:
Beissinger, SR, Wunderle, Jr., JM, Meyers, JM, Seather, B-E, and S Engen. 2008. Anatomy of a bottleneck: diagnosing factors limiting the population growth in the Puerto Rican parrot. Ecological Monographs 78: 185-203.
Christian, CS, Potts, TD, Burnett, GW, and TE Lacher, Jr. 1996. Parrot conservation and ecotourism in the Windward Islands. Journal of Biogeography 23: 387-393.
Christian, CS, Zamore, MP, and AE Christian. 1994. Parrot conservation in a small island-nation: case of the Commonwealth of Dominica. Human Ecology 22: 495-504.
Legault, A, Chartendrault, V, Theuerkauf, J, Rouys, S, and N Barre. 2011. Large-scale habitat selection by parrots in New Caledonia. Journal of Ornithology 152: 409-419.
Milius, S. Parrot survey finds poaching but also hope. Science News 159: 343.
Ortiz-Catedral, L and DH Brunton. 2009a. Nesting sites and nesting success of reintroduced reed-crowned parakeets (Cyanoramphus novaezelandiae) on Tiritiri Matangi Island, New Zealand. New Zealand Journal of Zoology 36: 1-10.
Ortiz-Catedral, L and DH Brunton. 2009b. Notes on the diet of the critically endangered orange-fronted parakeet (Cyanoramphus malherbi) on Maud Island. New Zealand Journal of Zoology 36: 385-388.
Snyder, NFR, Koenig, SE, Koschmann, J, Snyder, HA, and TB Johnson. 1994. Thick-billed parrot releases in Arizona. The Condor 96: 845-862.
Taylor, TD and DT Parkin. 2010. Preliminary insights into the level of genetic variation retained in the endangered echo parakeet (Psittacula eques) towards assisting its conservation management. African Zoology 45: 189-194.
White, Jr., TH, Collazo, JA, and FJ Viella. 2005. Survival of captive-reared Puerto Rican parrots released in the Caribbean National Forest. The Condor 107: 424-432.
A fan of dancing, but not baseball caps.
I had some time during a recent road trip to think about the topic for this month- many ideas came to mind as I wondered about this aspect of conservation or that issue of research, but I kept coming back to birds, maybe because they show up so often as you travel (such as the bluebirds and swallows at Antietam). And for some reason that I cannot explain, I started wondering about parrots.
My experience with these animals is largely limited to cleaning their cages (and I always appreciated that the macaws gave me a wide berth during those sessions, unlike the sulfur-crested cockatoos who seemed determined to take my broom). I did see some in the wild in Bolivia, which was fantastic, but they were generally at a distance. I know that they are social (the African Grey in Texas, although taking advantage of his time inside to learn the ‘Andy Griffith’ theme song, was much happier when returned to the outside aviary), intelligent, and can be quite single-minded, but I don’t really know much about parrot conservation, despite how common they are in zoos and as pets. I know that certain species have been introduced (intentionally or not) to new habitats, and there are some concerns about them as invasives, and I imagine that the pet and feather trades have had a big impact on wild populations, but I feel pretty vague about all of that, which seems strange when you consider how obvious they are (both in appearance and noise) in any habitat.
So this month I will be looking into parrot conservation around the world. Hopefully, I can develop a view of these birds that goes beyond aviaries and cages. If there is a species that is of particular interest to you, let me know and I’ll see what I can find- given the general popularity of birds, I’m sure there’s lots of information out there.
During the past few weeks, I’ve been looking into invasive aquatic plants- it’s clear that there are many species and that we are doing a good job of helping them find new habitats to exploit. It’s also clear that there are big differences between species in terms of impact and the locations where they pose a real concern. It is possible to eradicate invasive species, but that’s a long-term commitment that requires a certain amount of stamina, both fiscal and physical (a study in Nevada and California estimated that manual removal of milfoil cost $750-$1500 per hectare per treatment (Eiswerth et al. 2000)- and that needs to be sustained over multiple treatments). Prevention is a better goal here, but, since these invasives are already present, we’ll need to approach them from both angles- and there are many, many ways that we can all contribute to the campaign.
Stopping the spread:
- Learn to identify the target species- federal governments, state/provincial governments, and international bodies all have lists of invasive species with descriptions, some even have ‘ask the experts’ options for help if you are stumped. Maine, for example, has a list of common names of invasives to help you recognize them in other contexts, and the US government has an invasive plant atlas.
- If you are a boater/fisherman/outdoor enthusiast, be sure to clean and dry all equipment before transporting it between bodies of water- the USFWS recommends using hot or salty water to clean equipment and reminds you that pets can transport invasive species if they play in one body of water and then are not thoroughly dried before leaving the area (that was a new idea to me). Several states have already moved to ban felt-soled waders because they are harder to clean than the rubber-soled variety- check out the Invasive Species Action Network for more information on that and other angler concerns.
- If you have a home aquarium or water garden, be sure to research your plants and talk to your suppliers- a study in South Africa found that aquaria owners were better informed than the dealers who supplied them (Martin & Coetzee 2011), so spread the knowledge you have. And please consider using native alternatives for your home and garden- in Australia, there is a region-by-region resource that gives you the best alternatives for your area. And when it comes time to dispose of a non-native species, seal them in plastic bags and put them directly in the trash- we don’t want seeds getting into compost or roots surviving the trip to the dump.
Monitoring our progress:
Getting to the root of an invasion:
- Many regions have organizations with active invasive species removal programs (as well as planting of native species) with activities throughout the year- this is a chance to get your hands dirty and make a personal contribution to eradicating invasive aquatics. It’s short notice, but the Chesapeake Bay Program will be planting marsh grass on May 30- they have other events throughout the year. For those of you living around Boston, the Charles River Watershed Association works to protect that water body (water chestnut removal, anyone?).
Invasive species are a very big issue, and I’ve only looked at a small piece over the past few weeks. I think that effective prevention of their spread only works when everyone is informed and participates, and I think that removal of invasives really does require everyone to pitch in because a lot of work is needed. I’ve just scratched the surface here with regard to getting involved, so find an activity that appeals to you and get to it- this is a cooperative effort.
Works cited:
Eiswerth, ME, Donaldson, SG, and WS Johnson. 2000. Potential environmental impacts and economic damages of Eurasian watermilfoil (Myriophyllum spicatum) in western Nevada and northeastern California. Weed Technology 14: 511-518.
Martin, GD and JA Coetzee. 2011. Pet stores, aquarists and the internet trade as modes of introduction and spread of invasive macrophytes in South Africa. Water SA 37: 371-380.
As I mentioned in my last post, invasive aquatic plants are a big concern- although we are still learning about how they impact invaded ecosystems (and it’s not necessarily bad), we do know that plants such as water hyacinth, Spartina spp., and milfoil can clog waterways, change habitat, and alter faunal communities. And, as we become more aware of the influence of climate change, there are worries that invasive aquatics are just getting started.
How does climate change play into this? I learned during my research this week that it does, in part, depend on which species we are talking about. There is some agreement that climate change will probably facilitate access to new places (Hellmann et al. 2008; Rahel & Olden 2008). As Arctic ice retreats, ships will be able to use routes north of Canada and Alaska for greater portions of the year, and current routes around the world may shift if populations and resource needs change due to an altered environment. Another concern is that, as temperatures in northern lakes moderate, there may be more pressure to manage the fish populations for sport fishing (which can introduce exotic species) and increase recreational boater access to these sites (with all the hitchhikers from other water bodies that entails). Warming waters could also increase the amount of suitable habitat invasive species encounter- the growth of Caulerpa spp., for example, is related to water temperature (Occhipinti-Ambrogi 2007), so we could see successful invasions spreading out toward the poles as the world’s oceans heat up. It is also likely that, as we deal with our own concerns about climate change, we will help invasives move into new locations. Water scarcity may become an issue in new locations as precipitation patterns change, leading to the construction of more reservoirs- reservoirs both provide new locations for recreational activity which can lead to species introductions and create bodies of still water which can be more susceptible to domination by certain invasive species (Rahel & Olden 2008). So are we looking at continued worldwide conquest? Well, that’s a hard one to answer. A study in Australia that modeled the future spread of lippia weed (Phyla canescens) in riparian areas found that, although rising temperatures would hypothetically open new areas for colonization, changes in rain fall would make certain areas less suitable because there wouldn’t be enough water (Murray et al. 2012). And changes in ocean salinity (both higher in some locations and lower in others) have a role to play- when looking at the spread of Spartina alterniflora in northern China, He et al. (2012) determined that salinity levels had greater importance than competition from other plants in success or failure to invade a habitat.
(In case you were wondering what alligatorweed looks like.) Photo from: Robert H. Mohlenbrock. USDA SCS. 1991. Southern wetland flora: Field office guide to plant species. South National Technical Center, Fort Worth. Courtesy of USDA NRCS Wetland Science Institute.
However, there are also worries that invasives might actually help each other become dominant. A study in Connecticut found that invasive phragmites reeds actually helped native bullfrog larvae grow bigger and survive the larval stage better (Rogalski & Skelly 2012) which seems like a great thing, except that these same bullfrogs are invasive in the western US and phragmites there might help the frogs become completely dominant (when this type of synergy feeds and feeds upon itself, they call it ‘invasion meltdown’- what a bright future…). And water hyacinth, although having lower establishment, has higher growth in the presence of alligatorweed (Wundrow et al. 2012).
Do we have options for dealing with these invasives? Yes, although it will likely require sustained effort from everyone. Once again, effective management or eradication plans are species-dependent. Water lettuce is not cold hardy, so, in areas with ice cover in winter, manual removal can work to control it (of course, if global warming changes those winter patterns, we’ll need a new strategy) (Hellmann et al. 2008). Since hydrilla tubers can remain viable in soil for at least 4 years, it’s important to not only remove the plants that are there but also clear out the tubers (Doyle & Smart 2001)- this can be partially accomplished by drawing down the water level to encourage tuber sprouting and then exposing the tubers to desiccation, but you need to repeat the cycle multiple times plus use other removal techniques if you want to eradicate them. Treatment of phragmites along the coast of Cape Cod involved yearly herbicide starting in 2002 (Lombard et al. 2012)- by 2009, the phragmites stands had become less dense overall and were removed from some locations, but they estimated a few more years were still needed to eradicate the species from the area- that’s a long-term commitment and expense. And that same study that pointed out water hyacinth growth benefited from alligatorweed presence, also found that alligatorweed did better without water hyacinth- so if we clear out the water hyacinth, we could help increase the alligatorweed (‘tis a puzzlement).
So there’s a lot of work to be done with invasive plants, and plenty of room for each of us to help. For next week, I’m going to look into ways we can participate in invasive prevention, monitoring, and removal- we may not be able to turn back the clock on invasives, but we can try to limit their negative impacts.
Works cited:
Doyle, RD and RM Smart. 2001. Effects of drawdown and dessication on tubers of hydrilla, an exotic aquatic weed. Weed Science 49: 135-140.
He, Q, Cui, B, and Y An. 2012. Physical stress, not biotic interactions, preclude an invasive grass from establishing in forb-dominated salt marshes. PLoS ONE 7: e33164.
Hellmann, JJ, Byers, JE, Bierwagen, BG, and JS Dukes. 2008. Five potential consequences of climate change for invasive species. Conservation Biology 22: 534-543.
Lombard, KB, Tomassi, D, and J Ebersole. 2012. Long-term management of an invasive plant: lessons from seven years of Phragmites australis control. Northeast Naturalist 19 (Special Issue 6): 181-193.
Murray, JV, Stokes, KE, and RD van Klinken. 2012. Predicting the potential distribution of a riparian invasive plant: the effects of changing climate, flood regimes, and land-use patterns. Global Change Biology 18: 1738-1753.
Occhipinti-Ambrogi, A. 2007. Global change and marine communities: alien species and climate change. Marine Pollution Bulletin 55: 342-352.
Rogalski, MA and DK Skelly. 2012. Positive effects of nonnative invasive Phragmites australis on larval bullfrogs. PLoS ONE 7: e44420.
Rahel, FJ and JD Olden. 2008. Assessing the effects of climate change on aquatic invasive species. Conservation Biology 22: 521-533.
Wundrow, EJ, Carrillo, J, Gabler, CA, Hom, KC, and E Seimann. 2012. Facilitation and competition among invasive plants: a field experiment with alligatorweed and water hyacinth. PLoS ONE 7: e48444.
