Record-setting year for South Florida wading birds

Young Wood Storks eat a fish brought by a parent at Wakodahatchee Wetlands in Delray Beach, Florida. Photo by Marilynne Strazzeri

A record-smashing number of wading birds produced nests in South Florida in 2018, according to a report released today by the South Florida Water Management District.

During the 2018 nesting season (December 2017 to July 2018), an estimated 138,834 nests were initiated by the herons, egrets, spoonbills, ibises, and storks that nest in the Everglades and surrounding region.

Avian ecologist Mark Cook, one of the lead researchers, summarized the findings, writing:

“This is the largest annual nesting effort observed since comprehensive system-wide surveys began in South Florida in 1995 and is comparable with the historical large nesting events that occurred in the 1930s and ’40s. It surpasses the previous banner nesting season (2009) by over 51,000 nests and is approximately 3.5 times the 10-year average (39,850.6 nests).

 “All species exhibited increased nesting effort during 2018. Of note was the large number of nests produced by the White Ibis (100,784 nests), which was almost five times the 10-year average (20,444.1 nests) and more than double the previous record of 47,001 nests in 2009. The federally threatened Wood Stork produced 5,777 nests, which was 2.4 times the 10-year average (2,448.1 nests) and the third largest nesting effort for storks since the 1960s. Even the small herons of the Egretta genus (Snowy Egret and Tricolored Heron), which have shown sharp declines in nest numbers over the past decade, showed a moderate improvement in nesting effort in 2018.”

Cook also notes that nesting success was relatively high. Between 48 and 77 percent of study nests fledged at least one offspring. “Tens of thousands of young birds were produced, which will help boost population levels for future nesting years,” he said.

“Historically, about 90 percent of Everglades wading birds nested in the estuarine region of Everglades National Park,” the summary says. “The proportion of nests in this region in 2018 (33 percent) was one of the highest recorded in decades. Though this proportion fell short of the 50 percent restoration target, the magnitude of nesting (approximately 40,000 nests) was considerably greater than it has been in recent years. This suggests that the coastal ecotone retains the capacity to support large numbers of nesting birds when hydrologic conditions are suitable. 

Fortuitous climatic and hydrological conditions

“Nesting during 2018 was a marked improvement compared to recent years primarily because of an unprecedented series of fortuitous climatic and hydrological conditions that were highly conducive to promoting prey availability. Nesting was preceded by record-breaking wet conditions for extended periods across large areas of the landscape, which provided ideal conditions for growing prey populations. This was then followed by a winter-spring dry season that was drier than average and provided the necessary water level recession rates and water depths for concentrating prey and providing wading bird foraging habitat until late in the dry season.

“Historical nesting data from the pre-drainage Everglades reveal that nest numbers naturally fluctuate considerably among years in accordance with hydrologic conditions. A single year of nesting data is therefore insufficient to understand the health of the Everglades or its populations of nesting wading birds, and instead we need to consider long-term nesting patterns. The long-term data provided by this annual wading bird report reveal that several nesting responses have improved in the Everglades over the past 20 years, but some measures are not improving or are getting worse.”

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