An Eastern bluebird in a typical pose, scanning for moving insects on the ground in a field with a few scattered trees. These striking birds are found in these habitats year-round but in winter they turn into frugivores, feeding primarily on fruits and berries. Photo by E. Vernon Laux
Longest days - bring on the bird feeder blues
The most often asked question that has been phoned in or come up in discussions about birds over the past two weeks has been, what is going on at my bird feeders. Many feeder keepers report that although they have a tremendous amount of activity at seed, suet and hummingbird feeders all year long, about ten days ago the birds stopped coming to visit the feeders. What is going on?
The answer is that all birds present on the Island right now are attempting to raise more birds. This is intense, non-stop, and tiring work that requires the birds to find and procure protein and calcium rich foods for developing little birds that are growing bones, muscle, feathers, beaks, and claws, and the only way for this to happen is to feed them lots of insects, spiders, caterpillars if they are land birds; fish if they are ospreys; and rabbits, squirrels, and rats if they are red-tailed hawks, and so on. Hummingbirds forego much of their nectar diet when feeding young and gather prodigious numbers of insects, especially spiders to feed their young.
The second most asked bird-related question is whether birds eat the horrid caterpillars that are swarming over trees and shrubs again this year. Most land birds will not eat hairy caterpillars. Most of the moth caterpillars infesting area trees are not hairy and the birds are indeed feeding their young as many as they can eat. The problem is there are too many caterpillars at the same time, overloading any and all natural possibility of birds eating enough to solve the problem. There are increasing numbers of both black-billed and yellow-billed cuckoos on the Island that feast on both hairy and smooth caterpillars. They have been having a good series of years as their favorite food has been super abundant.
Breeding is a dangerous and risky proposition for birds. Despite the seemingly endless array of things that can go wrong for a bird tied to a nest and eggs or young for a few weeks, the birds do indeed often succeed in raising young. Birds are never more vulnerable than during the nesting season as these most mobile of creatures become predictable and easy pickings for terrestrial mammals that actively seek out nests. Birds have developed some defenses, primarily the flight response, to avoid predators, but many nests fail because of predation.
A big problem all over the eastern half of the continent is the steadily increasing number of a medium-sized blackbird called the brown-headed cowbird. These birds are brood parasites - they lay their eggs in other birds' nests. In most cases the host species has no defenses to deal with a foreign egg and incubate it raising the young as its own.
The young cowbird hatches first, quickly rolls the other eggs out of the nest and gets all the food at the expense of a year's worth of some little bird not producing any of its own kind. Not nice! It is a huge problem for a large number of woodland species. Just as the European cuckoos have earned a nasty reputation, cowbirds are deserving of a worse one.
Ultimately it is not the cowbirds doing but mankind's that has caused the spread of this disastrous species. Restricted to the prairies ecosystem on the North American Great Plains, following the massive herds of buffalo, they quickly took advantage of European settlement that cleared land and made roads giving the cowbirds a toehold into formerly dense woodland. They quickly spread eastward along the trails cut through the forest by westbound immigrants, laying eggs in the nests of virtually every bird smaller than them, against which these species had no prior experience or defenses. They are now a major reason for the decline of many songbirds in the eastern half of the continent.
Enough about cowbirds and let's not talk about starlings or English sparrows either. It is too easy to get caught up in all the things that have gone wrong by way of introduced species and man's alterations of the landscape. Instead, let's focus on some positives.
Locally, eastern bluebirds were gone from the Island but with the help of one Paul Jackson of Edgartown, the birds are now doing well and are fairly common on the Vineyard. Ditto for ospreys thanks largely to Gus Ben David, formerly of Felix Neck and now of the World of Reptiles. Starting in the 1960s, he began to erect nesting platforms and it turns out the availability of a nest site was the limiting factor. The population went from one pair to upwards of 80 pairs, all because of his efforts with the help of his friends and associates.
Baby birds are all around now. If you encounter any baby birds, just leave them alone. When you find one make sure if you are a cat owner that your keep it in the house. The adults stay in contact, vocally, and locate their young by contact calls. Just out of the nest they develop rapidly and in a couple of days will be fully capable of flight.
Young birds when they first leave the nest are still growing feathers, building muscles, and learning to fly. They are completely vulnerable to predators; especially domesticated feline ones, so a little timely help can go a long way. They do need protection from your cat, however, so keep it inside at this season of extreme vulnerability for birds. By keeping your cat in, the bird population will have a much better chance of breeding successfully near your home.
Until next week - keep your eyes to the sky!
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