An online resource based on the award-winning nature guide

Bird Diets

A Killdeer’s Diet

8-4-17 killdeer2 049A1132Ninety-eight percent of  a Killdeer’s diet  consists of animal matter.  Beetles, insect larvae, earthworms, grasshoppers and crayfish make up the majority of what a Killdeer eats. In the summer, adult beetles (see photo) and beetle larvae make up almost half of what they consume.

Much of the time we observe Killdeer they are running, stopping, waiting and then running again. This is typical feeding behavior. Another method of obtaining food consists of patting the ground or the bottom of a pond in shallow water with one quivering foot. Killdeer also engage in probing into mud and chasing prey, and they have been known to follow tractors in search of earthworms.

Food normally passes through a Killdeer’s digestive tract in about two hours, but the spore-bearing structures of some ferns that it eats take five to sixty hours. All birds have gizzards, where food is ground up. Some birds swallow grit to aid in the grinding process, and the Killdeer is one of them. It has been proposed that the sporocarps take longer to pass through a Killdeer because they are retained in the gizzard where they function as grit.

 

 

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Cedar Waxwings Feasting on Fruit

1-31-17-cedar-waxwing-049a3342

Cedar Waxwings are strictly fruit eaters in the winter, expanding their diet to include insects during the warmer parts of the year. As their name implies, one often finds these birds in areas where there are a lot of cedars, as they’ve historically fed on cedar berries in winter. However, they increasingly rely on the fruit of mountain ash as well as apple, crabapple and hawthorn in the Northeast. Waxwings run the risk of intoxication and even death after eating fermented fruit such as the apples pictured. In recent years Cedar Waxwings have started feeding on the fruits of invasive honeysuckles, a habit which ornithologists feel might be responsible for a shift in waxwing distribution as well as regional population increases.

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Small Birds Beware of Sharp-shinned Hawks

coopers-and-blue-jay-by-jeannieShort, powerful, rounded wings and a relatively long tail enable Sharp-shinned Hawks to maneuver in dense cover in pursuit of small birds, which compose 90% of their diet. Small mammals and insects are consumed, but not nearly as frequently as birds. The size of the birds eaten range from hummingbirds to Ruffed Grouse. Long legs and toes (especially middle toes) enable individuals to reach into vegetation and large eyes enhance its ability to catch fast-moving prey.

Sharp-shinned Hawks are familiar sights to those of us with bird feeders – this species is responsible for 35% of 1,138 predation incidents reported at feeders in continent-wide survey. In this photograph, a Blue Jay is successfully warding off an attack by a juvenile Sharp-shinned Hawk. (Photo by Jeannie Killam.)

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Attracting Fruit-eating Birds

7-11-16  birds and oranges 519.jpgThere are many birds, such as waxwings, that have a frugivorous (strictly fruit-eating) diet.  The only time they usually expand their diet to include insects is during the breeding season, when growing hatchlings require high amounts of protein for proper development.  Others, such as orioles, show a marked preference for fruit but also eat significant quantities of other foods.  All of these birds play an important role by spreading fruit seeds to distant areas either by caching food or distributing the seeds through their droppings.

Bird lovers often put out seed to lure birds in for a closer look (a practice discouraged during the summer in black bear country), but there is an equally effective magnet for some species, and that is fruit. (Due to the high sugar content, little nutrition and potential bacteria growth in jelly, it may be best to provide fruit over jelly.) Grapes often attract Northern Mockingbirds, Eastern Bluebirds, Cedar Waxwings, Gray Catbirds, Scarlet Tanagers, Rose-breasted Grosbeaks, House Finches and American Robins.  Raisins and currants (soaked in water overnight) appeal to Northern Mockingbirds, Gray Catbirds, Eastern Bluebirds, Cedar Waxwings and Eastern Towhees.  Species that find orange halves hard to resist include Red-bellied Woodpeckers, Northern Mockingbirds, Brown Thrashers, Baltimore Orioles, Scarlet Tanagers, Gray Catbirds and Rose-breasted Grosbeaks.  (Photo: Gray Catbird (left), female Red-bellied Woodpecker (middle) and female Baltimore Oriole (right) enjoying breakfast at The House On The Hill Bed & Breakfast, Greenfield, MA.)

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American Crow Bills Used As Tools

1-13-16  American crow tracks 147American crows obtain most of their food on the ground as they walk along in search of seeds, insects, frogs, snakes, bird nests and small mammals. Their hunting techniques are varied and most involve the use of their bill. In search of invertebrates, crows will probe the soil with their bill, flick aside leaves, dig in the soil and even lift cow paddies. They fish for tadpoles and dig nearly an inch deep with their bill for clams. In winter, their foraging continues and as these tracks indicate, when the snow is only a few inches deep they will walk around and around in a given area, probing tufts of grass for hibernating insects, mice, voles, or any other form of life these opportunists find.

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Pileated Woodpecker Droppings

11-12-15 pileated droppings 015Pileated Woodpeckers usually defecate frequently during the day at their foraging sites. As they pry off long slivers of wood to expose carpenter ant galleries, the wood chips pile up on the ground. A substantial pile usually indicates that the woodpecker has been working long enough at this site for there to be some droppings in the pile.

Pileated Woodpeckers eat ants, primarily carpenter, and beetle larvae throughout the year. Fruit and nuts are eaten when available. The primary food shifts seasonally, with fruit mainly in the fall, carpenter ants in the winter, wood-boring beetle larvae in early spring, and a variety of insects in the summer.

Like humans, birds excrete metabolic waste products, mainly nitrogen, which remains after food is broken down. Humans excrete waste nitrogen as urea in urine, which is diluted with water. Birds, needing to be as light as possible for efficient flight, do not have heavy, water-filled bladders. They excrete nitrogen as a chemical called uric acid in a concentrated form with no dilution necessary. The white outer coating of bird droppings is uric acid. The insides of the droppings are the actual feces, or the indigestible parts of a bird’s diet. A Pileated Woodpecker’s droppings at this time of year consist of bits of carpenter ant exoskeletons and a surprisingly small amount of wood fiber (see insert). Birds simultaneously evacuate uric acid and feces from an opening just under the tail called the cloaca or vent.

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Tree Swallow Nestlings Well Fed

7-21 tree swallows 068Tree Swallow parents begin feeding their four to seven nestlings as soon as they hatch, and they continue doing so until their young depart the nest and sometimes for several days afterwards. The adult carries food in its bill and places it directly into the open mouth of a begging nestling. The small insects gathered by the parent may be formed into a rounded ball, or bolus, which they hold in their mouth or throat (often not visible to an observer). Both parents feed the nestlings, together averaging about ten to twenty deliveries per hour. During periods of peak nestling demand, parents may feed as many as 6,000 to 7,000 insects in a single day. (Thanks to Jeannie Killam and Terry Ross for photo op.)

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