White-breasted Nuthatches Nesting
White-breasted Nuthatches are one of the 85 species of North American birds that are classified as cavity nesters. Although the young of birds nesting in cavities are protected from the elements, they are still vulnerable to predators.
White-breasted Nuthatches have an unusual strategy for discouraging uninvited guests. They “bill-sweep” with an object, usually a crushed insect, in their bill, sweeping back and forth on the tree both outside and inside the nest, often for many minutes at a time. It’s thought that chemical defense secretions from the crushed insect may discourage squirrels from entering the cavity. (Red-breasted Nuthatches apply sticky conifer resin to both the inside and outside of their nesting cavity, which presumedly serves the same purpose.)
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Where Are All The Birds?
Even though signs as well as sightings of active bears are plentiful, and black-oiled sunflower seeds are an open invitation for them to visit and potentially become “nuisance” bears, many devoted bird-lovers have already hung out feeders in hopes of luring feathered friends closer to their home. Throughout northern New England so few birds have been attracted to these feeders that they have remained full, some not having been refilled since September. Our usual fall and winter visitors appear to have all but vanished, and concern has been growing amongst those who feed birds.
Those familiar with bird feeding habits know that in the fall, when seeds are abundant, feeder visits by resident birds typically slow down. However, this year, at least anecdotally, appears to be extreme in this regard. Warm weather extending into November certainly has lessened birds’ food requirements. But having sunflower seeds sprout in your feeder before the need to replenish them arrives is unusual, if not alarming.
Dr. Pam Hunt, Senior Biologist in Avian Conservation at New Hampshire Audubon, recently shared some of her personal research with the birding world (UV- Birders). Hunt has conducted a weekly, 10 km-long, bird survey near Concord, NH for the past 13 years. In addressing the current concern over a lack of feeder birds, she extracted the data she had accumulated on 12 common birds (Mourning Dove, Downy Woodpecker, Hairy Woodpecker, Blue Jay, Black-capped Chickadee, Tufted Titmouse, White-breasted Nuthatch, White-throated Sparrow, Dark-eyed Junco, Northern Cardinal, House Finch, American Goldfinch) over the last 13 falls, focusing on the period between Oct 1 and Nov 15. After extensive analysis, Hunt concluded that there has not been a dramatic decline in the number of birds this year, relative to the averages of the past 13 years. One cannot argue with scientific evidence (except for, perhaps, #45), but it does seem mighty quiet on the western (northeastern?) front this year.
The Nuthatch Name
Have you ever thought about the derivation of the Red- and White-breasted Nuthatch’s common name? It comes from their habit of wedging a nut, acorn, etc. into a tree’s bark, and by repeatedly striking the nut, “hatching” or exposing the seed within it.
Many of these seeds are then stored in bark furrows for later consumption. In one study it was found that nuthatches spend more time caching husked than unhusked seeds (71% of sunflower seeds cached were husked). This inevitably would lower the expenditure of energy and time spent when consuming the cache later in the season. Hiding time, and time and distance flying from feeders to cache sites were longer when nuthatches hoarded husked than unhusked seeds, perhaps indicating their increased value to the birds. (photo: White-breasted Nuthatch with husked sunflower seed)
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White-breasted Nuthatches Raising Young
White-breasted Nuthatches maintain their pair bond throughout the year. In the spring, after mating, the female builds her nest, lining the tree cavity (natural or old woodpecker hole) with fur, bark, and lumps of dirt and then making a cup nest of grasses and bark inside the cavity. She then lays her 5 – 9 eggs and incubates them for roughly two weeks, during which time the male brings her food.
After the eggs hatch, both parents provide their nestlings with food until they fledge. Initially the female remains with the young, and the male brings food for both her and the nestlings. His trips become more frequent during the first few days, starting at about 7 trips an hour and increasing to 13. After three or four days the female also participates in food gathering, as much or more than the male.
The average day length in June is approximately 15 ½ hours. At 26 deliveries/hour (13 per parent) that comes to a total of around 400 foraging trips a day for the majority of the 26 days before White-breasted Nuthatch nestlings fledge. Impressive, especially when you consider that many of these trips involve not only delivering food but also removing the nestlings’ fecal sacs.
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Birds & Burdock
The 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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Bark Scaling
There are two main ways that woodpeckers and occasionally other birds remove bark in search of insects beneath it. One is bark sloughing, where a bird pries off the entire dead layer of bark on a tree (see NC post on 12/5/14). Another method of locating insect larvae that both woodpeckers and nuthatches employ is the removal of individual scales of bark. This is referred to as bark scaling. The pictured hairy woodpecker has removed much of the bark of a dead eastern hemlock using this method.
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