The Nesting Birds on Lake Mango Bird Island, 2025

Chip Erwin

The bird nesting activity on Lake Mango Bird Island this spring and early summer is quite remarkable and locally important. During a recent survey conducted by a Tampa Audubon biologist, over 400 pairs of birds of eleven species were observed courting, making nests, incubating eggs, or attending and feeding nestlings. Some fledged Great Blue Heron young-of-the-year and “branchling” Tricolored Heron young were also noted as they anxiously waited for their dedicated and patient parents to return to the island with food for their final growth spurt before becoming independent birds.

Two of the species nesting on Lake Mango Bird Island are listed by the Florida Fish and Wildlife Conservation Commission as “Threatened”, due to low population numbers in the state, Little Blue Herons and Tricolored Herons. An adult Roseate Spoonbill was also seen, although there were no indications that the bird was nesting. Roseate Spoonbills are also listed as “Threatened” by FFWCC because of the low population of only about 1500 pairs in Florida. All the birds nesting on the island are protected by the Migratory Bird Treaty Act, an international agreement that ensures birds can reproduce and successfully raise their young. This law is also enforced by the FFWCC.

The island is used as a bird nesting site by so many birds because it has no ground predators, such as raccoons, skunks, or cats. It is situated a fair distance from the shoreline in a lake with swimming alligators. The alligators patrol the area near the island, eating any young that fall from their nests or unwary adults along the shoreline. The presence of the alligators deters raccoons or other predators from swimming to the island and taking advantage of the current bonanza there of birds’ eggs and chicks. Mammalian predators are smart and aggressive and would gladly consume the eggs or chicks if they could safely access the island - but they know instinctively that there is danger in the water – the alligators on patrol. It is important that alligators remain as a part of Lake Mango’s ecosystem, because of the role they play in protecting the nesting birds on the island.

Because it takes so long for the wading birds to raise their young (25-30 days of incubation followed by 2-4 months of daily protection and provisioning of freshwater prey items to the growing chicks, depending on the species), it is not possible for the nests to be discretely hidden. As they grow, the young are noisy, a sign that the colony is not disturbed.

During the nesting period, one of the adult parents remains with the eggs or young to protect them from aerial predators as hawks, crows, other herons, or vultures. Parental “guard” duty also includes incubation, shielding the eggs and later the chicks from rain, shading them during the heat of the day, and keeping them warm during the cooler evenings.

In all, there is a lot of activity at the Bird Island. It is fine for boaters to slowly approach the island shorelines, keeping far enough away as not to disturb the normal behaviors of the birds, approximately 45 feet away. With binoculars, a person can watch what the birds are doing as they choose mates, build nests, lay and incubate eggs, and feed and protect their young without affecting the behavior of the parent birds or their young. It’s fine for boaters to watch and enjoy the spectacle of the nesting behaviors of the many birds on Bird Island, while making sure that the bird parents can do the vital work of raising their young without disturbance.

I believe we all enjoy watching the birds and wildlife on Lake Mango. But how many birds can you identify? My older sister is a member of Tampa Audubon and has arranged a few lake tours with some of their experts. The last tour was specifically to conduct a nesting count with Ann Paul, retired but a real expert. I have 2-part report from her.

Project Colony Watch Report

Lake Mango Island Colony Survey

Survey Date – May 7, 2025 Survey Time – 7:15-8:00 p.m.
Conditions – slight west wind, warm evening, fair weather
Surveyors – Chip and Trudy Erwin, Ann Paul

Numbers represent nests observed.
Anhinga 25
Great Blue Heron 8, including one brood of two large young and a singleton large young
Great Egret 13
Snowy Egret 15
Little Blue Heron 25, including a yearling in breeding condition
Tricolored Heron 15, including one “branchling” young
Cattle Egret 45
Black-crowned Night-Heron 5, as represented by 5 young-of-the-year fledges
Yellow-crowned Night-Heron 1
White Ibis 300, about half courting, the other half on nests
Glossy Ibis 35
Total 442 nests*

In addition, we observed an adult Roseate Spoonbill, so it might be advantageous to carefully look for spoonbill nesting during later season surveys.
Little Blue Herons, Tricolored Herons, and Roseate Spoonbills are listed “Threatened” by the Florida Fish and Wildlife Conservation Commission (FFWCC), based on low numbers in Florida. All the species nesting on the Lake Mango Bird Colony Island are protected from disturbance during nesting by the international Migratory Bird Treaty Act, enforced in Florida by FFWCC.

Disturbance to the Lake Mango Bird Colony Island should be curtailed while birds have nests, eggs, and young. Plantings of cypress trees in the fall (October-November) would support future nesting activity, although there are sufficient tree structures to accommodate multiple species nesting there. The presence of some alligators should be tolerated in the lake, as their presence discourages predators as raccoons from swimming to the island, protecting the nesting birds.

*Not all the nests could be counted as many were located behind thick bushes and screening vegetation. Therefore, this is a low total number and more pairs are nesting here than were counted by this survey.