americas-rarest-heron

Are populations of America’s rarest heron declining?

Audubon to help track populations with FWC grant

By Ann Paul & Mark Rachal, Audubon Florida’s Coastal Islands Sanctuaries

Like many of Florida’s iconic birds, populations of reddish egrets (Egretta rufescens) were nearly wiped out during the late 1800s when hunters relentlessly collected them for the lucrative plume trade. By the beginning of the 20th century, there were no reddish egrets nesting in Florida. Only a small population persisted in south coastal Texas. Reddish egrets were observed nesting in Florida Bay in 1938 and the state’s population has recovered slowly, although it still remains small.

After an absence from Tampa Bay of nearly 100 years, reddish egrets returned as a nesting species to the west central Florida coast in 1974, with two pairs observed in Hillsborough Bay south of Tampa at Audubon’s Richard T. Paul Alafia Bank Bird Sanctuary. The Tampa Bay population slowly increased, peaking in 2004 with 98 pairs spread across 15 islands, where they nest in small numbers among other herons and ibis in wading bird colonies.

The largest nest concentration remains at the Alafia Bank, although nesting there dropped dramatically starting in 2006. One factor in that decline may be disturbance during courtship by nature photographers attempting close-up shots of “high-color” courting reddish egrets and roseate spoonbills. Tour leaders are bringing groups of photographers to the sanctuary during the peak period of reddish egret courtship and potentially driving off birds that would otherwise nest undisturbed. (See Bay Soundings, baysoundings.com/legacy-archives/spring2013/commentary.php)

Today the major portion of the state’s population is centered in Florida Bay, with sparse nesting on either side of the state northward to secondary population centers in the Tampa Bay/Pinellas County and Indian River/Mosquito Lagoon regions. Recent surveys at historically large colonies indicate that reddish egrets may be experiencing a pronounced population decline in Florida and throughout their range.

Florida’s State Wildlife Action Plan and FWC’s draft A Species Action Plan for Six Imperiled Wading Birds both point out key conservation data gaps for reddish egrets, specifically information about the current population trends and distribution within Florida. The rarest heron in North America, the state also ranks reddish egrets as a “Species of Greatest Conservation Need.” The reddish egret is state-listed as an imperiled species because of the extremely small population size (likely less than 800 mature individuals) and potentially negative population trends because it depends upon very specific estuarine habitats for nesting and foraging.

This spring, Audubon Florida’s Coastal Islands Sanctuaries (FCIS) staff is participating in a state-wide survey of reddish egrets as part of a grant funded through the Florida Fish and Wildlife Conservation Commission’s State Wildlife Grant Program.

While FCIS has compiled ongoing surveys of colonial birds in the Tampa Bay region, information on the distribution and abundance of reddish egrets along the rest of Florida’s coastline is sparse. The aerial surveys typically used for colonially nesting wading birds are ineffective for reddish egrets because of the species’ dark plumage and preference for nesting in the sub-canopy of coastal islands, out of sight from the air.

They occur along coastlines of the southeastern United States, Mexico, Colombia, Venezuela, and a few Caribbean islands. Roughly 10% of the estimated global population of reddish egrets (2,500-3,000 breeding pairs) resides in Florida.

Reddish egrets typically nest in mixed-species colonies on small islands in estuaries and on barrier islands, and sometimes as solitary nesters. They select under-canopy arboreal nest sites where branches hang over water, often on the edge of islands behind a thicket of leaves and branches that obscure their nests but where they can see out of the island. In Florida, the species typically occurs as dark morph birds with a smaller population of white morph birds, about 5% of Florida’s
population.

Surveying during the peak nesting season (typically December to March in Florida Bay and south Florida and late February to May in central coastal Florida) should result in accurate population counts of adult birds, as their activity will be centered at specific colony sites for several months during breeding.

Biologists undertaking the state-wide survey this spring will survey from motorboats or other craft off-shore of small islands and conduct ground counts of some larger islands. In addition to Audubon’s FCIS staff, survey participants include biologists from the FWC’s Florida Wildlife Research Institute in Gainesville, Audubon’s Everglades Science Center, and the Avian Research and Conservation Institute headquartered in Gainesville.

Several nesting sites in Tampa Bay and Pinellas County will be surveyed for nesting reddish egrets.

This project will provide the state with a rigorous, validated survey method to monitor reddish egret population trends and provide a baseline for future statewide surveys. The data will also be used to quantify nest-site selection patterns of reddish egrets so managers can focus on protecting important habitat features.

It’s not likely that reddish egrets will ever return to their historic populations because they rely upon habitat that has suffered permanent damage, but that makes protecting the remaining habitat even more important.

Project Colony Watch

Motivated birders and land owners across Florida are adopting and protecting waterbird colonies in their own communities. The larger waterbirds, including reddish egrets, pelicans, herons, ibis, Spoonbills and storks, nest in colonies to avoid predation by ground predators.  This behavior allows volunteers to help protect many pairs raise their young.  Guidance provided by Audubon’s Florida Coastal Islands Sanctuaries (FCIS) staff through Project Colony Watch allows volunteers to scientifically survey their local colonies, provide appropriate key information to agency staff, and work with land managers to ensure that nesting birds remain undisturbed during this vulnerable life stage.  Local waterbird colonies provide critical nesting sites for 25 species in Florida, ten of which are listed by the state.  This spring, volunteers coordinated by Tampa Audubon, St. Petersburg Audubon, Sarasota Audubon, Clearwater Audubon, Eagle Audubon, West Pasco Audubon, and Lake Region Audubon surveyed and learned about colonies in their neighborhoods and were actively involved in preventing impacts to nesting birds.  These volunteers have become the local "wardens," biologists, and advocates for their nesting colonies. Each volunteer makes a difference for the wildlife where they live, plus experiences the enjoyment of watching birds nest and raise their young.  If you would like to get involved with a Colony Watch project in your area, please contact Audubon Sanctuary staff Mark Rachal or Ann Paul at 813/623-6826.

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