The Lure of Bird Lores
An avian field mark that warrants special attention this time of year is the color of a bird’s lores — the area between a bird’s eye and bill on both sides of its head. In some birds, especially wading birds, lores change color quite dramatically during the breeding season.
Because birds can see blue, green and red (like humans) as well as UV light, and because the change takes place just as the breeding season begins for birds, the change in lore color, often to a more vibrant hue, is thought to play a part in attracting a mate. (The bills, legs and feet of some birds also change color at this time.)
At the height of the breeding season, Great Egret lores go from yellow to an emerald green. Green Heron lores turn from a yellowish-green to a bluish-black. Snowy Egrets (pictured) lores become bright pink. This happens to both sexes ever year.
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Green Herons’ Versatile Necks
Most of the time Green Herons appear to be stout, compact herons. When perched or stalking, they tuck their neck into the contours of their body and appear quite small (see inset). Only when threatened or when striking prey is the true length of a Green Heron’s neck revealed. If startled, a Green Heron will stretch its neck way out, most likely in order to appear large and formidable to a potential predator. When hunting for prey, it can extend its neck an inordinate distance (see photo). A specialized vertebra in their neck enables them to strike at prey with a tremendous amount of force. Some scientists compare the Green Heron’s extendible neck to that of certain dinosaurs, from which they are thought to have evolved.
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Tadpole Maturation
The eggs of Wood Frogs, the earliest species of frog to breed in the Northeast, are just hatching and tiny Wood Frog tadpoles can be found swimming about at this time of year. This Green Heron is devouring a tadpole, but it is anything but tiny – certainly not a Wood Frog tadpole. How can this be?
The answer is that the tadpole that the Green Heron caught did not hatch this spring – it hatched last summer. Unlike Wood Frogs and Spring Peepers that mature in roughly two months, Green Frogs and American Bullfrogs can take two or even three years to metamorphose into adult frogs. By their second summer they are of substantial size. The Green Heron has caught a Green Frog or Bullfrog tadpole that has overwintered and would probably have matured this summer.
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Green Herons Starting To Migrate
Green Herons breed throughout the eastern half of North America. After their nesting season is over they tend to wander, often to more favorable foraging areas. This dispersal merges gradually into a protracted fall migration for birds in the Northeast, beginning around the end of August, with most birds having left by mid-October.
Most Green Herons from eastern United States migrate south to winter along the Gulf of Mexico, Florida, Caribbean islands, Mexico, through Central America to northern South America. We usually see our first Green Herons returning in mid-April, earlier than other herons. This may be due to their crepuscular feeding habits, which gives them a longer span of time to feed each day.
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Green Heron Feet
The structure of a Green Heron’s foot lends itself to a life of wading at the water’s edge while foraging for food and not sinking into the sand. Three long toes pointing forward and one pointing backward create a considerable amount of surface area, and the more the surface area the less pressure that is placed on the sand. Webbing between its outer toes adds to the snowshoe effect (and also aids the heron when it dives below the surface of the water for prey and must swim back to shore).
This foot structure comes in handy when wading in shallow water, standing on emergent vegetation or perched a low-hanging branch at the water’s edge. As testimony to this, the pictured Green Heron spent an entire morning navigating from water lily pad to water lily pad foraging for fish, insects, frogs and other aquatic life.
Juvenile Green Herons Becoming Independent
Green herons are typically solitary and secretive birds, but if you find one, you often have an extended period of time to observe it, as they often slowly stalk their prey, or pose statue-like, sometimes for minutes at a time, while waiting to strike at a fish, frog or invertebrate. Three characteristics tell you that the green heron in this photograph is a juvenile: the few tufts of down that remain on its head, its streaked neck (adults have solid rufous necks) and its yellow legs (adults have orange legs).
After fledging when about three weeks old, they can soon fly. The juvenile fledglings continue to be fed by the adults for a period of time and are taught how to forage for fish. Green herons are one of very few bird species that are known to occasionally use a tool (insects, earthworms, twigs, feathers) to catch their food – they simply drop the lure and wait for small fish to appear. (A wonderful video of a green heron successfully using bread for this purpose can be seen at https://www.youtube.com/watch?v=Porp5v5lLKk.)
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