In my post last week I talked about three of the big challenges facing colonial seabirds: habitat loss, invasive species, and changing food resources. I spent the last few days reading about ways to combat these problems, plus gaining insight on other issues related to seabird survival. The good news is that we are continually getting better information about what effects seabird populations, and often we can do something to help. The bad news is that they face a laundry list of problems.
Brown pelicans seem pretty happy to use the pond in front of a newly constructed back marsh area which will eventually fill in with plants and add area to a barrier island
When it comes to habitat loss, while we can’t always stop it in the first place (limiting development of an area is one thing, stopping sea level rise is totally different…) we have had success at creating new habitat for seabirds to use. Here in Louisiana (and elsewhere) material from dredging canals and harbors has been used by terns and skimmers (Mallach and Leberg 1999) since it is initially bare of vegetation- the problem, of course, is that plants eventually fill in the area, so the process needs to be repeated to keep creating habitat. Just about every island that I work on has had some type of restoration project and a variety of bird species, including brown pelicans, least terns, and spoonbills use these areas for nesting. And we’ve been able to create nesting habitat on a tiny scale as well– African penguins dig their own burrows, but islands that have been harvested for guano don’t have enough material for that, so the birds nest on open ground which puts eggs and chicks at risk from predators, high temperatures, and rain. When researchers put out artificial nest boxes on Robben Island, South Africa, penguin nesting success went up (Sherley et al. 2012).
We’ve also had some success at addressing the issue of invasive predators. Off the western coast of Mexico, eradication efforts starting in 1996 had removed invasive predators and herbivores (who trample soil and denude landscapes) from 26 islands by 2008 (Aguirre-Muñoz et al. 2008). By starting with islands that had smaller areas and fewer invasive species, projects helped build up knowledge for more complex situations. By 2008 at least 201 bird colonies had been protected at a cost of $58 per hectare for each invasive species removed- not bad, right? Of course, these successes depend on keeping those invasives from coming back, so educational campaigns were the next step in the process so that local people moving between the mainland and islands don’t reintroduce any species. A recent review of threatened seabird species suggested that, of 968 islands with threatened seabirds, 37% had invasive species (Spatz et al. 2014), so we’ve got a ways to go, but we’re definitely developing more effective strategies at removing the threat of invasive predators and herbivores.
The problem of changing food resources is a bit trickier to tackle. To begin with, some of those changes are happening in response to global changes in climate, so that’s a long-term process. In addition, we’re not exactly sure how flexible some birds are at changing foraging strategies or how they will compete with each other. There is an EU proposal to end fishery discards by 2019- previously discarded fish would be retained for use (Bicknell et al. 2013). While this would make the fisheries more sustainable, it would mean that birds currently utilizing discards would not have that food resource anymore. Generalists will probably be just fine- there are, after all, other fish in the sea. But specialists might be in trouble if the stocks they depend on have already been depleted. And there is concern that gulls and skuas may turn to more egg and chick predation. So, we’re going to have to see how this pans out.
Another seabird issue that was mentioned several times in the literature was light-induced mortality, especially for fledglings. For nocturnal species, urban lights can be disorienting and may draw birds away from the coast and into urban environments. In Hawaii, shearwater mortality has been reduced through dampening the lights by putting shields around them and a “Save Our Shearwaters” campaign which rescues and releases birds (Duffy 2010). Similarly on Reunion Island, a rescue program plus public education has reduced mascarene petrel mortality (Corre et al. 2003).
So seabirds are facing big challenges and we are getting better at understanding and meeting those challenges. Although some of these problems may seem very far away from us, there are bound to be ways that we can contribute to seabird conservation. In my final post of the month, I’ll take a look at our options.
Works cited:
Aguirre-Muñoz A, Croll DA, Donlan CJ, Henry III RW, Hermosillo MA, Howald GR, Keitt BS, Luna-Mendoza L, Rodríguez-Malagón M, Salas-Flores LM, et al. 2008. High-impact Conservation: Invasive Mammal Eradications from the Islands of Western México. AMBIO – J. Hum. Environ. 37:101–107.
Bicknell AWJ, Oro D, Camphuysen K (C. J., Votier SC. 2013. Potential consequences of discard reform for seabird communities. J. Appl. Ecol. 50:649–658.
Corre ML, Ghestemme T, Salamolard M, Couzi F-X. 2003. Rescue of the mascarene petrel, a critically endangered seabird of réunion island, indian ocean. The Condor 105:387–391.
Duffy DC. 2010. Changing seabird management in Hawai’i: from exploitation through management to restoration. Waterbirds 33:193–207.
Mallach TJ, Leberg PL. 1999. Use of dredged material substrates by nesting terns and black skimmers. J. Wildl. Manag. 63:137–146.
Sherley RB, Barham BJ, Barham PJ, Leshoro TM, Underhill LG. 2012. Artificial nests enhance the breeding productivity of African penguins (Spheniscus demersus) on Robben Island, South Africa. Emu 112:97–106.
Spatz DR, Newton KM, Heinz R, Tershy B, Holmes ND, Butchart SHM, Croll DA. 2014. The Biogeography of Globally Threatened Seabirds and Island Conservation Opportunities. Conserv. Biol. 28:1282–1290.