The field work associated with the 115th Audubon Christmas Bird Count (CBC) has now been completed. More than 2000 “count circles” are surveyed each year in December and January and the number of species and the number of individual birds are recorded. Such a survey has been conducted in what is known as the Wekiva River count circle for more than 25 years. The Wekiva River count circle is divided into 15 zones based on landmarks and natural boundaries such Interstate 4 and the Little Wekiva River.
This year 130 different species and more than 25,000 individuals were documented. Over 60 people spent hundreds of total hours on foot, in canoes, in golf carts and cars across urban, rural and wilderness areas that have been similarly surveyed for more than two decades.
Every year, unique species of birds are detected and trends in populations of certain species are noted, and this year was no exception. I perused the historical data and found some interesting information about some individual species and trends from the recent past in the Wekiva River count circle, Florida statewide counts and across the nation.
Black-bellied whistling ducks are relatively new to the Wekiva CBC, and to the Florida CBC for that matter. Although a recent entry, several hundred black-bellied whistling ducks have been observed in most of the last five years in the Wekiva count. Ring-necked ducks are still consistently the most common species of waterfowl on the count.
Northern bobwhites (bobwhite quail) have all but disappeared from the count. They have been observed in two of the last five counts, and each of these was represented by one covey of less than 10 birds. This is reflective of a national trend for bobwhites, and for other birds that require substantial areas of open habitats. Their reductions in numbers are related to landscape-level changes across the Southeast. Loggerhead shrikes and eastern meadowlarks have followed a similar pattern, and their total numbers in the Wekiva count have declined over the recent past.
The CBC data managers have compiled historic data that can be “normalized” by calculating the numbers of an individual species observed per party (or group) hour of birding. Using this approach, the numbers of birds counted can be compared even if a larger number of people participated or a greater number of count circles were surveyed. For northern bobwhites across its range, about 0.3 birds were counted per party in 1975. In 2013, this number had dropped to less than 0.05 birds per party – about a 90% decline (see the chart below), and none were observed in the Wekiva count circle in 2014. Numbers are less dramatic, but comparable for loggerhead shrikes and meadowlarks across their ranges.
About 10 different species of wading birds are present in virtually every zone within the Wekiva CBC. They seem to be taking full advantage of man-made ponds as well as natural wetlands across the count circle. One of those birds – the white ibis – is famously nomadic, and consequently their numbers have varied from about 300 to more than 1500 on individual counts. Their habit of seeking saturated soils and shallow marshes with exactly the right level of inundation effects the kinds of habitat, and the location across Florida where they might occur.
During this year’s count we documented 38 bald eagles – the most ever found in the Wekiva count circle. Like most CBCs across Florida, a relatively abundant bald eagle population has been confirmed during recent Christmas counts. We have observed a relatively consistent number of adults and juveniles over the last decade, with total numbers averaging a little less than 25 individuals on each count over the last five years.
In general, rock pigeons, an urban adapted non-native bird, has increased as urbanization has expanded within the Wekiva count. A cousin of the rock pigeon, the Eurasian collared-dove emerged in the account within the last 10 years, but despite apprehension about the potential for an ever-expanding population, their numbers have remained low – less than 10 individuals between 2009 and 2013.
Hairy woodpecker have not been common in central Florida for decades, and none have been observed in the Wekiva count since 2009. Red-bellied woodpeckers are the most common woodpecker every year, and the easily-heard pileated woodpecker is detected in virtually all of the 15 zones within the Wekiva count circle every year.
It is interesting how certain species occur in relative abundance during some years, even though they are absent, or occur in diminished numbers during other years. For example, there have been dramatic fluctuations in numbers of American robins (12, 500 individuals in 2011 and a few more than 1500 in 2014), tree swallows (ranging from 0 in 2009 to more than 2800 this year in the last 5 years) and cedar waxwings (with a low of 25 in 2010 and a high of 925 in 2013).
Yellow-rumped warblers are consistently the most common warbler species, and we typically count approximately 1000 individuals. Palm warblers are the second most common with an average of approximately 275 birds observed each year. These warbler species are followed in abundance by pine warbler and common yellowthroat.
Quite a few species of sparrows are detected during each year’s count. Chipping sparrows and savannah sparrows are seen virtually every year. Others occur infrequently, potentially due to their relative scarcity, quiet deportment in the winter and their ability to blend in with the natural environment. Bachman’s sparrow, swamp sparrow and grasshopper sparrow are seen virtually every year, while Henslow’s, song, Lincoln’s and white-throated sparrows are observed infrequently.
There have been a consistent number of blackbirds and grackles observed over the years. We typically see more than 500 each of red-winged blackbirds, common grackles and boat-tailed grackles each year. Even though they are a substantial nuisance in other portions of the United States, the nest predator and non-native brown-headed cowbird is not common within the Wekiva count circle. We have only seen five individuals in the last three years.
In general, we detect between 115 and 130 species in the Wekiva River count circle each year. This is generally affected by weather – sunny, windless, cold days frequently produce the greatest numbers of observations – and the number and experience of birders in the field. For the Wekiva River count, we typically have between 40 and 55 people participating in approximately 15 separate parties. Some of the counts are markedly more urban than they were 20 years ago, while other parties spend virtually the entire day’s count in natural areas under public ownership.
The 2014 Wekiva CBC yielded a few rare birds that are not typically observed during this count in December. These included magnolia warbler, bufflehead, pine siskin, Virginia rail, summer tanager, barn swallow, horned grebe and common goldeneye.