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ECOVIEWS: Where are the pelicans?

January 20, 2019

A friend recently asked why he no longer saw many brown pelicans on the coast at Daytona Beach. He has been visiting that area of Florida for more than 40 years and in the last couple has seen far fewer than in earlier years.

My first response was to ask whether he had been there during the same season each year and on the same stretch of beach. Many birds have seasonally consistent patterns of flight from their roosting or nesting sites to feeding areas. He said yes: same time and place. I shelved that explanation and considered what could have changed environmentally. I turned to coastal ecology expert Meg Hoyle of Botany Bay Ecotours on Edisto Island. Meg has extensive experience in coastal habitats and would likely have some suggestions.

She said she knew of no general problem with brown pelican populations, noting that the species had increased dramatically in overall numbers since the environmental disaster known as DDT, when countless numbers of species declined. Brown pelicans were almost extirpated from the southern coasts of North America before pesticide regulations began being enforced in 1972. She explained that ground-nesting brown pelicans often choose sites on small offshore islands or sandbars, some only a few inches above sea level. Such habitats may be subjected to ocean overwash during storms. She did not have any specifics about pelicans in the coastal areas of Florida but had had experience with the response of pelicans to Hurricane Hugo several years ago in South Carolina. Nesting and roosting habitats had been destroyed and the birds moved to other sites in the region.

One possibility in Florida is that Daytona Beach pelicans historically nested on local islands that became uninhabitable by ground-nesting birds following Hurricane Matthew in 2016. If a prime nesting habitat had been flooded and the surface scoured by wave action followed by sand loss, it would have resulted in a slightly reduced elevation. If the former nesting site were no longer suitable for nesting because of flooding, the pelicans would have sought other areas. Their foraging flight patterns would have changed as well and perhaps would no longer include the same sections of beach as before.

The choice of nesting habitats in the Atlantic and the Gulf where brown pelicans live is an excellent example of the tenuous ecological relationship many animals have with the environments they depend on for survival. A sandy island susceptible to saltwater flooding but inaccessible at low tide for raccoons and foxes would provide protection from these and other terrestrial predators that would eat the eggs, the birds or both. Meg mentioned another hazard that exists for ground-nesting shorebirds in addition to the flooding potential of such islands. Avian ticks. These insidious bloodsuckers can be abundant on offshore islands where coastal birds nest. Infestations can reduce hatching success as well as the health of pelicans. The life cycle of the ticks includes their remaining on the island, waiting patiently for pelican nesting season to return. An upside of saltwater overwash during a major storm is removal of all ticks from the island. If the island gradually builds up through new sand deposits, a temporarily tick-free nesting site becomes available and the pelicans return. Saltwater flooding can be bad or good for a pelican, a clear example of nature’s irony.

I will point out that the ecological understanding of the interaction between avian ticks, brown pelicans and island overwash is supported by extensive research on coastal habitats. My suggestions about the effect of Hurricane Matthew on Daytona Beach pelicans are speculative and hypothetical. Systematic records of pelicans kept by local bird enthusiasts in Florida may reveal another explanation peculiar to the region. However, if loss of nesting habitat and subsequent relocation is the explanation, squadrons of pelicans should eventually return to the old habitat. With the elimination of parasites, the number of pelicans on future visits to Daytona Beach may be even higher than before.

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