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Black-capped chickadee foraging behavior

 

figure1Figure 1. Our study species, the chickadee.

The black-capped chickadee, Poecile atricapillus, is one of the most common birds in Canada. It is classified in the family Paridae of the order Passeriformes, and has a range extending across southern Canada and the northern United States.3 Most people are familiar with these birds or have at least heard their distinctive “chickadee-dee-dee” calls.[1] Black-capped chickadees call to communicate information such as recognition of other flocks and predators. Other birds such as nuthatches, woodpeckers, and kinglets also respond to chickadee alarm calls.[2]

Watch our video recording of chickadees calling.  Be careful not to confuse it with the nuthatch call! 

The black-capped chickadee is easy to recognize by its distinctive plumage. As its name suggests, it has a black-capped head with a black throat, white cheeks, gray back, and beige to white belly. Juveniles and adults of both sexes have similar plumage, making them difficult to tell apart at first glance. [3] Black-capped chickadees are typically 12 to 15 cm in length with a wingspan of 16 to 21 cm and weight of 9 to 14 grams. 1 They have a round body shape due to their short necks, large heads, and short beaks. Black-capped chickadees eat insects, seeds, and berries.2 They are common year-round visitors to bird feeders and are known for being bold and inquisitive, sometimes even taking food from a human hand.1

 figure-2Figure 2. A chickadee’s unique allure.

Black-capped chickadees cache food in order to survive the winter. Instead of sitting on bird feeders for extended periods of time, they often make many brief visits to take single seeds and cache them for later use. Chickadees have a good memory to remember where seeds are hidden; however, this memory is short-term. Research done by Christine L. Hitchcock and David F. Sherry in 1990 showed a decline in the recovery of cached seeds after periods of 1, 28, 56 and 84 days.[4] The hoarding of seeds is mainly observed in October[5], which was perfect for our research project. As winter approaches and temperatures drop below zero, chickadees excavate roosting holes in rotting wood. They do not migrate, but may travel long distances when reproduction is high.2 During the winter, chickadees form flocks and group territories. There are two hypotheses as to why this occurs: To protect seeds hidden the previous autumn and/or to control access to nests during breeding season.[6]

Watch our video of chickadees taking one seed at a time.

Figure 3 . On the left, a white breasted-nuthatch at our feeder.  On the right, a white breasted-nuthatch sharing the feeder with black-capped chickadees.

In addition to our love of birds, the black-capped chickadee’s distinctive appearance, abundance at bird feeders, and year-round presence made it the perfect study species for our group. For our research question, we wanted to determine how cover and vegetation type affects black-capped chickadee foraging behavior. To answer the research question, we constructed ten identical bird feeders from 2-liter soda bottles and installed them on shepherd’s hooks at locations with four different combinations of cover and vegetation type: edge of deciduous forest, edge of coniferous forest, 15 meters into field bordered by deciduous forest, and 15 meters into field bordered by coniferous forest. We chose locations far enough apart from one another to ensure independent sampling. We filled the feeders with sunflower seeds once per week during the first two weeks of October in order to get the chickadees accustomed to the feeders, and on the day before each observation day in the third and fourth weeks. We divided each of the two observation days into four blocks of 30 minutes. During each block, we each observed one feeder and counted how many times black-capped chickadees landed on it. Other behavior, such as preemptive landings in the grass and aborted landing attempts, as well as other species present were also recorded. Each feeder was thus observed four times in total, but the block numbers during which each was observed and its observers were randomized.

figure-4 Figure 4. Our feeder set-up.

Kathryn M. Frens conducted a similar experiment in 2010 for her Master’s thesis at University of Michigan[7]. In her experiment, bird feeders with hulled and unhulled sunflower seeds were set up in open field and in forest, and the duration of visits by black-capped chickadees, tufted titmice, white-breasted nuthatches, and American goldfinches were compared. Interestingly, she found that chickadees spent the same amount of time foraging in the field as in the forest. However, her experiment differs from ours because she measured duration rather than frequency, looked at heavy forest cover instead of edge, and did not compare different forest types.7 Our prediction is that black-capped chickadees will prefer the edge over the field due to increased protection from predators. Since it is autumn and deciduous trees are losing their leaves, the chickadees may prefer coniferous forest over deciduous for the same reason. Due to time constraints, we were not able to test different distances from the edge, but this could be a topic for a future study.

 

Bibliography

 

[1]Society, N. G. (n.d.). Black-Capped Chickadees, Black-Capped Chickadee Pictures, Black-Capped Chickadee Facts – National Geographic. Retrieved October 27, 2016, from http://animals.nationalgeographic.com/animals/birding/black-capped-chickadee/

[2]The Cornell Lab of Ornithology. (n.d.). Black-capped Chickadee. Retrieved October 27, 2016, from https://www.allaboutbirds.org/guide/Black-capped_Chickadee/id

[3]Seattle Abundon Society. (n.d.). Black-capped Chickadee. Retrieved October 27, 2016, from http://www.birdweb.org/birdweb/bird/black-capped_chickadee

[4]Hitchcock, Christine L, and David F. Sherry. “Long-term Memory for Cache Sites in the Black-Capped Chickadee.” Animal Behaviour. 40.4 (1990): 701-712. Print.

[5]Smulders, T V, A D. Sasson, and T J. DeVoogd. “Seasonal Variation in Hippocampal Volume in a Food-Storing Bird, the Black-Capped Chickadee.” Journal of Neurobiology. 27.1 (1995): 15-25. Print.

[6]Smith, David C, and Buskirk J. Van. “Winter Territoriality and Flock Cohesion in the Black-Capped Chickadee Parus Atricapillus.” Animal Behaviour. 36.2 (1988): 466-476. Print.

[7] Frens, K. M. (April, 2010). Effects of food type and patch location on foraging: a field test of optimal foraging predictions [thesis]. University of Michigan.

 

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One comment on “Black-capped chickadee foraging behavior

  1. It is mentioned in your post that you predict chickadees will prefer feeders close to vegetative cover due to their ability to hide should a predator appear. What species prey on chickadees? Accipiters are known to take out larger birds like blue jays and sparrows, but chickadees are so small that I have to wonder whether it would be worth it for a predator to take the effort to hunt such a small bird. Do you know?

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