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Black-capped Chickadee

Birds & Burdock

2-15-16 bird caught on burdock by Holly BroughIMG_5814The phenomenon of North American birds being killed by becoming entangled in Common Burdock (Arctium minus) has been documented since at least 1909, when one observer (in A.C. Bent’s compilation) described finding a multitude of Golden-crowned Kinglets in Common Burdock’s grasp:

They were visible in all directions, scores of them sticking to the tops of the clumps on the most exposed clusters of heads. The struggle had ended fatally for all that I saw, and its severity was evidenced by the attitudes of their bodies and the disheveled condition of their plumage. I examined a number of the burdock heads to determine that attraction had brought the kinglets within range of the hooks, and found insect larvae of two species present in considerable abundance.

Typically this phenomenon involves birds that are seeking either insects that are inhabiting the seed heads, or burdock seeds. The birds’ feathers get caught by the hooked bracts (modified leaves) that surround both the flower heads and seed heads of burdock. Small birds such as kinglets, gnatcatchers, goldfinches, nuthatches, hummingbirds, chickadees, warblers and siskins are the usual victims, but larger birds, including a Blue-headed Vireo and a Barn Swallow, have been caught as well. Most of these birds were found with their wings and tail spread, and caught by many parts of their bodies. The more they struggled, the more their feathers became entangled. Victims are not limited to birds — in 1925, a dead bat was discovered caught in a patch of burdock. (Photo by and thanks to Holly Brough)

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Goldenrod Ball Galls Provide Important Source of Winter Food for Downy Woodpeckers

12-11-15 goldenrod ball galls 058A number of insects cause goldenrod plants to form galls – abnormal growths that house and feed larval insects. The Goldenrod Ball Gall is caused by a fly, Eurosta solidaginis. The fly lays an egg on the stem of a Canada Goldenrod (Solidago canadensis) plant in early spring, the egg hatches and the larva burrows its way into the stem; the plant reacts by forming a gall around the larva. The larva overwinters inside the gall, pupates in late winter and emerges in early spring as an adult fly. Prior to pupating, the larva chews an exit tunnel to, but not through, the outermost layer of gall tissue. (As an adult fly it will not have chewing mouthparts so it is necessary to do this work while in the larval stage.)

Downy Woodpeckers (and Black-capped Chickadees) have discovered this abundant source of winter food, and dine on the larva after chiseling a hole into the gall. Downy Woodpeckers tend to make a tidy,narrow, conical hole by pecking, while Black-capped Chickadees tend to make a messy, large, irregular hole by grabbing bits of the gall with their bill and tugging them free. While woodpeckers prefer larger galls that are located high on goldenrod plants growing near wooded areas, these are not the only factors taken into consideration.

A woodpecker extracts the fly larva through the tunnel the larva excavates prior to pupating, as this facilitates rapid removal of the larva. Downy Woodpeckers can determine whether or not a gall has an exit tunnel, and if it doesn’t, they usually abandon the gall without drilling into it. The likelihood of smaller parasitic wasp larvae occupying the gall (and a plump fly larva not being present) is much greater if there is no exit tunnel, and these smaller prey apparently are not always worth the woodpecker’s time or energy.

NB: Correction: this week’s Mystery Photo was of a Gray Birch (Betula populifolia) bract, not a Paper, or White, Birch (Betula papyrifera) bract. While similar, there are differences between these two species of birch that I should have recognized (especially when looking at the leaf!). Thanks to Kathy, an alert blog reader, who caught this error.

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Black-capped Chickadees Starting to Build Nests

3-13-15  black-capped chickadee and Emma's hair 067At least two to four weeks before one would expect to find a black-capped chickadee building a nest, one was busily collecting hairs shed by my chocolate lab yesterday. In addition to fur, chickadees line their nest with grass (not available yet here), down and moss (hard to come by with two feet of snow still on the ground). Chickadees are able to nest this early in part because they nest in cavities, which offer them protection from the elements. Not having bills strong enough to hammer out cavities in living trees, chickadees rely heavily on rotting stumps for nest sites — the wood in them is punky and easy to remove. Birch, poplar and sugar maple snags and stumps are preferred nesting trees. If you want to provide chickadees and other birds with nesting material, take advantage of the fact that dogs and cats are shedding now, and recycle their fur.

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Tufted Titmice Caching Seeds for Winter Consumption

tufted titmouse2  379Tufted Titmice and Black-capped Chickadees are in the same family (Paridae), and share several traits, one of which has to do with securing food. They are both frequent visitors of bird feeders where they not only take seeds and soon thereafter consume them, but they also collect and cache food throughout their territory for times when there is a scarcity of food. Tufted Titmice usually store their seeds within 130 feet of the feeder. They take only one seed per trip and usually shell the seeds before hiding them.

In contrast to most species of titmice and chickadees, young Tufted Titmice often remain with their parents during the winter and then disperse later in their second year. Some yearling titmice even stay on their natal territory and help their parents to raise younger siblings.

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Honeybee Scavenger

2-10-14 chickadee & bee33 174If the weather warms up sufficiently in January or February, honeybees take advantage of it and use this opportunity to leave their hive to rid themselves of waste that they have accumulated since their last flight and to remove the bodies of dead honeybees. They don’t fly very far before dropping either their waste or their dead comrades on the snow. This ritual is quickly noted and taken advantage of by animals that are not hive dwellers and need constant fuel in order to survive the cold. Black-capped chickadees are one of these animals – the chickadee in this photograph repeatedly landed on the hive body, and if a dead bee was available at the hive entrance, the chickadee helped itself to it. Otherwise it would survey the snow in front of the hive and then dart down to scoop up a bee in its beak before flying off to a branch to consume its nutritious meal. (Note dead bees at the hive opening, awaiting being taken on their final flight. Screening keeps mice out, but allows bee to enter and exit.) Thanks to Chiho Kaneko and Jeffrey Hamelman for photo op.

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Bird Feeding – Does It Foster Dependency?

1-15-14 bird feeders 139Decades ago birds remaining in the Northeast in the winter almost exclusively survived on weed seeds and insects they gleaned from crevices in tree bark. Today, nearly one-third of American adults provide about a billion pounds of bird seed each year, to say nothing of suet, seed cakes, etc. Should we be worried about creating a population of food-dependent wintering birds? Studies suggest that this is not the case. Researchers (this is going to sound cruel) removed feeders from woodlands where Black-capped Chickadees had been fed for the previous 25 years, and compared survival rates with those of chickadees in a nearby woodland where there had been no feeders. They documented that the chickadees familiar with feeders were able to switch back immediately to foraging for natural foods and survived the winter as well as chickadees that lived where no feeders had been placed. Not only did the feeder-fed birds not lose their ability to find food, but research also showed that food from feeders had made up only 21 percent of the birds’ daily energy requirement in the previous two years. This is not to say that there aren’t negative aspects to feeding birds, such as window collisions, disease, house cats, etc., but one thing luring birds to our houses for a closer look doesn’t do is destroy their innate ability to find food. (Photo is of a Red-breasted Nuthatch.)

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Did you know…

11-20-13 black-capped chickadee IMG_0107Black-capped Chickadees actually refresh their brains once a year. According to Cornell’s Laboratory of Ornithology, every autumn Black-capped Chickadees allow brain neurons containing old information to die, replacing them with new neurons so they can adapt to changes in their social flocks and environment.

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