Fishing Methods Of Birds With Spear-shaped Bills
How do herons, egrets, bitterns, kingfishers, loons and other fish-eating birds with spear-shaped bills capture their prey? Do they use their bill as a spear and pierce through a fish, or do they grab the fish between their mandibles? You often read about one of these birds “spearing” a fish. However, a majority of these birds, most of the time, do not spear fish, but open and shut their bills fast enough to capture a fish in them — the spear shape of their bill lends itself to the tong-like action it performs. In addition, its shape enhances the movement of the bill through the water as the bird dives (its head or body) into the water to grasp the fish between its upper and lower mandibles.
One exception to this rule is the Anhinga, which does run its bill (which is equipped with backward grooves to prevent slippage) through fish in order to capture them. After spearing a fish, an Anhinga then shakes it vigorously off its bill, tosses it in the air, and catches and swallows it headfirst. (Photo: Great Blue Heron)
American Crow Bills Used As Tools
American 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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Barred Owls Courting
Barred Owls call year-round but their vocalizations increase and expand in February when courtship begins. No longer are their calls limited to their year-round “who-cooks-for-you — who-cooks-for-you-all.” Males and females engage in “duets,” as well as many other vocalizations, including cackles, hoots, caws and gurgles. Those who sleep with open windows may feel like they are in the middle of a jungle inhabited by hundreds of raucous monkeys.
Barred Owl courtship is not strictly vocal. Male Barred Owls display by swaying back and forth and raising their wings, while sidling along a branch in close proximity to a female. Courtship feeding and mutual preening also occur prior to copulation. The nights of February are filled with amorous avian calls and gestures.
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Wood Drilling Adaptations
Woodpeckers have begun their courtship drumming and they continue to excavate trees for food. Both of these activities involve a woodpecker’s head striking a tree’s surface at speeds up to 13 – 15 mph, and continuing to do so at over 100 strokes per minute. To sustain this kind of blow against a tree, woodpeckers have a number of skull adaptations, including strong yet lightweight skulls and bills, a network of bony supports within their skull, extra calcification of the portion of the skull nearest the tip of the bill, cushioning cartilage joining the bones between the skull and the beak, shock-absorbing neck muscles and a brain that is packed very tightly into the brain cavity.
A woodpecker’s brain, however, isn’t the only part of its anatomy that is adapted for drilling wood. A woodpecker’s nostrils are narrow slits (not circular, as in many birds) and are covered with bristly feathers that prevent wood chips and dust from entering them. Special cells on the end of its bill are constantly replacing material lost due to drilling. This keeps the chisel-pointed bill strong and resilient, while allowing it to be sharpened with every blow. And finally, less than a second before a woodpecker’s bill contacts wood, a thickened nictitating membrane closes over its eyes, protecting them from flying wood chips. (Photo: male hairy woodpecker)
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Canada Geese Switch Diet to Berries & Grains
During migration and throughout the winter, Canada Geese are highly gregarious, often gathering and feeding in flocks that consist of over a thousand geese. Almost exclusively herbivorous, they are efficient grazers, having serrations on their stout, flat bills. During summer they feed primarily on grasses and sedges. Considered a nuisance by many people with large lawns Canada Geese are attracted to these lawns not only because they can digest grass, but also because they have an unobstructed view that allows them to detect approaching predators. During and following migration, berries (especially blueberries) and agricultural grains including sorghum, corn and winter wheat make up most of their diet. When you see them in cornfields, they are feeding on fallen kernels as well as corn still on dry cobs — they are very good at removing the kernels.
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Common Loon Chick Update
The fluffy, black loon chick that was the subject of Naturally Curious posts a couple of weeks ago is a month old this week (original photos were taken several days before posting), and it has undergone several transformations. Two weeks ago the black down of the newborn chick was replaced with a second coat of down that is brown in color. Between three to four weeks of age, its body elongated and its bill began to lengthen. In another week or so, the first gray contour and flight feathers will begin to replace the down, a process that takes about three weeks.
Both parents are very attentive and are providing as many fish and crayfish as the chick can consume, sometimes making the chick dive for its meal, sometimes not. Because one egg failed to hatch, the lone chick receives all of both parents’ attention, guaranteeing a full stomach. It isn’t unusual to see both parents dive, come up with fish in their bills, and deliver their catch simultaneously to their chick.
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Belted Kingfisher Snags, Stuns & Swallows Prey
Watching the hunting antics of a Belted Kingfisher can be highly entertaining. They often swoop down from a branch to grab prey which is near the surface of the water and they are also one of few birds capable of hovering– beating their wings while staying stationary long enough to focus on prey in the water. Once they’ve grabbed their prey, which is mostly fish, but also crustaceans, frogs, snakes, young birds and small mammals, in their pincer-like bill, the fun really begins. The kingfisher flies to a nearby perch with its prey in its bill and then proceeds to pound the prey against the perch with repeated sideways movements of its head. The kingfisher does this in order to stun the fish (or other prey) so that it can eventually turn it and swallow the fish head first. The kingfisher in this photograph was giving the crayfish it just captured a real beating before devouring it (head first).
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Hooded Mergansers & Feeding Adaptations
Although most of New England has Hooded Mergansers year round, we see them most frequently in the spring and fall, when Canadian-nesting individuals are migrating north. They stop to re-fuel in wetlands where they are well adapted for capturing and eating fish, insects and crayfish. The nature of the changes their eye lenses can make, coupled with the high degree of transparency of the membrane that covers their eyes under water give them superior vision under water. Their success in holding onto the struggling prey they capture is greatly increased by the serrated edges of their slender bill. (Photo: female Hooded Merganser)
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Evening Grosbeak Bills Changing Color
Breeding season changes in a bird’s physical appearance can involve more than a set of new feathers. The colors of birds’ feet, legs and bills can also change in different seasons. One transition most people are aware of is the European Starling’s bill which is black in winter and turns yellow as the breeding season approaches. Male and female Evening Grosbeaks also undergo a change in bill color, from bone-colored in the winter, to a greenish hue in the spring. Hormones are largely responsible for these pigmentation changes which often play a role in courtship behavior. Usually change in the color of the bill is most pronounced among birds which retain the same plumage color and pattern throughout the year, such as starlings and Evening Grosbeaks. (Photo-female Evening Grosbeak)
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Hairy and Downy Woodpecker Bills
Distinguishing Hairy Woodpeckers (Picoides villosus) from their smaller relatives, Downy Woodpeckers (Picoides pubescens), can be challenging if you don’t have a chance to view both species at the same time. The easiest way to tell them apart is to note the relative size of their bills. The Hairy Woodpecker’s bill is proportionately much larger than the Downy Woodpecker’s – it’s almost as long as its head — whereas the Downy Woodpecker’s bill is not nearly as impressive. Although a Downy Woodpecker can’t drill or probe as deeply into trees as a Hairy Woodpecker, it does have at least one advantage due to its overall smaller size; it is light enough to balance on the stems of goldenrods, which usually aren’t strong enough to support Hairy Woodpeckers. It is here that Downy Woodpeckers drill for overwintering goldenrod fly larvae inside goldenrod ball galls – a popular winter snack for this species.
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