Status of Wading Bird Populations of the Hillsborough River Watershed

摘要

The diversity and abundance of bird populations are often proposed as indicators of the quality of their habitats. For wetland systems, considerable attention has been devoted to the use of 'colonial waterbirds' as bioindicators (Kushlan 1993, Erwin and Custer 2000). Waterbirds seem to offer many advantages to observers. Most are large and easily identified, and are active during daylight hours. Many are not secretive, and may become quite tame in areas of chronic human activity like parks and recreation areas. 'Colonial' waterbirds offer an additional advantage: they nest in groups. Often colonies are very conspicuous, which allows observers to locate nesting sites and count or estimate numbers more efficiently than if the birds were solitary nesters. At least 31 species of waterbirds occur within the Hillsborough River Watershed, Florida (hereafter, HRW), including 19 that typically nest in aggregations or colonies and 12 that are solitary nesters. Nineteen species nest within the HRW, including 14 'wading birds' (herons, egrets, ibis, spoonbills and storks, plus Sandhill Crane and Limpkin). Ten of the 14 wading birds are colonial. Most of these species feed largely on fish and other aquatic organisms, and therefore forage in coastal waters, lakes, rivers, and other wetland systems. Restated, these species depend importantly on healthy wetland systems. It might be suspected, then, that population estimates or indexes of selected species, if compiled over a period of years, might serve as useful indicators of the health of local wetland systems. This report summarizes what is known about breeding populations of wading birds within the HRW, evaluates the existing data as a potential indicator of the health of the watershed, and offers suggestions for the design of monitoring programs of breeding or foraging wading birds that might advance ecosystem management goals.