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Posts tagged “Anas platyrhynchos

American Black Ducks Vs. Mallards

2-27-19 black ducksAmerican Black Ducks (Anas rubripes), found year-round in all parts of New England except for northern Maine, are nearly identical to Mallards (Anas platyrhynchos) in size, shape and voice. Both have rounded heads, thick bills, and bulky bodies. Like other dabbling ducks they sit high in the water with their tails high. These two closely related species often keep company with each other and it can be challenging to tell them apart, but it is possible to distinguish them with some certainty.

Most of the year male (drake) Mallards have a distinctive iridescent green head, a white neck ring and a yellow bill. However, the female (hen) Mallard’s plumage is very similar to that of both drake and hen Black Ducks. One of the most dependable ways to tell these two species apart is to look for the dark chocolate-colored body of the Black Duck, which is noticeably darker than the hen Mallard’s. At rest, the Black Duck is a uniform very dark brown from the bottom of its neck to its tail. The hen Mallard is a much lighter brown in this area, and in addition has a pale whitish patch on the belly. The color of the bill can also help with identification — the hen Mallard’s bill is orange and black, whereas the Black Duck’s bill ranges from a dusky yellow (drake) to a drab olive (hen) color. All of these identification clues go out the window when hybrids of these two species are encountered! (Photo: American Black Duck drake (L) and hen (R) )

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Make Way For Ducklings

5-26-14 mallard & ducklings  470After having spent a month or so incubating her eggs, the mallard hen begins to hear her ducklings vocalizing from inside their eggs, roughly 24 hours before they start to hatch. She responds with quiet calls, and begins turning the eggs frequently. Within 36 hours the ducklings crack open (“pip”) their eggs with the help of an egg tooth that is lost soon after they hatch. The down of the ducklings dries within 12 hours and often the morning after her young hatch, the hen leads them to water (not necessarily the closest water to the nest). She encourages them to follow her by quacking up to 200 times a minute as they travel over land to their watery destination. The ducklings can feed on their own, consuming mostly invertebrates and seeds. Once in the water, if the ducklings start to scatter, the mother can be heard repeatedly and softly quacking to her brood to gather them around her. She will continue to provide them with cover and warmth for the next couple of weeks, especially at night and during cold weather.

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Birds’ Feet

When I saw these mallards swimming in a frigid brook yesterday the first thought that came to mind was how cold their feet must be.  Exactly how do birds avoid getting their legs and feet frostbitten?  We’ve all seen birds standing on one foot while the other leg is pulled up under their feathers, where it warms up. This is one way, but not the only way, birds protect their feet from freezing. Birds’ feet are mostly bone and tendons, so, unlike mammals, they have a limited supply of nerves, blood vessels or muscles to freeze.  Their feet are also covered with scales which, like our hair, aren’t living tissue and thus are less susceptible to freezing. Some birds, including waterfowl, gulls and penguins, have what is called countercurrent heat exchange — in their legs, arteries and veins run parallel and in contact with each other. As the warm blood of the arteries enters the legs, the heat is actually transferred to the returning cold blood of the veins. This allows the cooler blood to get heated up before re-entering the body, which prevents a lot of heat from being lost to the cold air.  Under very warm conditions, the countercurrent heat exchange mechanism can be bypassed.