Few sights in suburbia cause quite the commotion that occurs when newcomers see their first flock of white ibis. The striking white birds with their distinctive orange-red bills are relatively common in the Tampa Bay region where they’re also known as the “gardener’s friend” because mole crickets, chinch bugs and grubs are among their favorite foods.
Still, white ibis are listed as a “Species of Special Concern” because their populations have declined by as much as 70% in the last 35 years. Although they were historically hunted for both their striking white feathers and their meat, the biggest threat today is loss of habitat and human disturbance of their nests.
The birds nest in coastal locations including Clearwater Harbor and the Alafia Bank. Their chicks, however, can’t tolerate the saltwater crustaceans their parents eat – they must have food harvested from freshwater ponds and marshes or garden pests. That means some birds must travel 15 to 20 miles inland several times a day to feed what the Audubon Society’s Ann Paul calls “feathered alimentary canals.”
Like many nesting birds, white ibis have evolved to take advantage of typical weather and water conditions. “In the summer, rain falls and waters spread across the marshes, where wetland invertebrates and little fishes take advantage of all that detrital material to reproduce like crazy,” Paul explains. When ponds and marshes dry up during the expected winter dry season, those food sources are concentrated in smaller, shallow areas where birds can easily capture food to feed their growing chicks.
The number of nesting pairs in Tampa Bay is somewhat dependent upon how successful white ibis have been in the Everglades where weather patterns are slightly different. “It’s still speculation, but it looks like when they fail in the Everglades, they come up here,” she said. “We don’t have vast expanses of wetlands like the Everglades, so they depend upon the Chinese checkerboard of small wetlands that still exist in the Tampa Bay region.”
Although the numbers fluctuate from year to year, an average of 8500 pairs of white ibis nest every Spring at the Richard T. Paul Alafia Bank Bird Sanctuary, the largest colony in Tampa Bay. The health of the chicks is dependent upon the quality and proximity of wetlands available to their parents, Paul said. “We’ve lost 50% of our wetlands since the 1950s and even when we leave wetlands, we’ve impacted the way they drain.”
Stormwater retention ponds, for instance, have replaced many small wetlands that once drained slowly to Tampa Bay. With their steep sides, many retention ponds are useless to the short-legged white ibis that can’t forage in deep water. “Hillsborough County has one of the best wetlands protection agencies in the nation, but the white ibis are still struggling,” she notes.
Article originally published Winter 2010.
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