Field Observation 3: Social Behavior and Phenology

I walked a ~ two mile loop in Centennial Woods on Saturday, 3/23 from 1:30 to 2:45. The weather was fair, with light-moderate winds, 50% cloud cover, and temperatures around 32° F. It was snowing in the mountains, and there was ~3 inches of fresh wet snow on the ground and clinging to tree limbs in the woods.

I heard BCCH making contact calls (high-pitched chips) and some love songs (chee-dee, chee-dee). I also heard a few territorial calls (chick-a-dee-dee-dee). The contact calls seemed to be a sort of "background noise," accompanying feeding and movement through the canopy of a stand of mature pines. The territorial calls and some louder chips were heard when I "pshh"ed in the vicinity of this small flock. I believe this sound works because it could represent a range of animals' alarm calls. It sounds kind of like a chipmunk or squirrel that is irritated about something. Small birds listen to one another and to other animals in their environment to detect danger or things out of the ordinary. This sound seems to replicate that type of cue, which explains why it can be met either with increased interest or a rapid departure from the area, depending on how it is perceived.

I noticed that contact calls generally accompanied movement from one foraging site to another, and that this movement sometimes seemed to involve wing flares that were more flashy than would simply be necessary for changing feeding location - this suggests to me that what I heard as "contact calls" can also serve an assertive function in establishing dominance hierarchies at food resources. Another sound that seems to serve a communication function was the drumming of a Pileated Woodpecker, which I heard at a distance but was still loud and clear. It must have found a good hollow tree to use as a drum. This sound communicates territoriality, which makes sense given the time of year, when birds are generally beginning to establish breeding and feeding territories.

A small Brown Creeper I observed made very high pitched, single notes (tseee, tseee). I thought I heard another individual responding, which suggests to me that these calls served a contact function. The Brown Creeper's foraging behavior involved frequent movement among small and medium sized trees, on which it spiraled up the trunk, apparently feeding on something in the bark. I did not quantify the intensity of this feeding, but it seemed somewhat desultory, especially given how much of the bird's time was spent calling and moving as opposed to feeding (about 2:1). I frequently saw the Brown Creeper in the same area of a tree as a BCCH, but they seemed to effectively partition the resource by utilizing different parts of the tree - the Brown Creeper stayed on the trunk, while the BCCH stayed on smaller side branches.

The behaviors observed in the Brown Creeper make sense given both the time of day and the time of year. In early afternoon on a bright, somewhat warm spring day, the Brown Creeper has presumably reached a positive energy balance and is now foraging to build up stores for night time. However, given the relatively mild weather and the length of the day now that we are past the equinox, it makes sense that the individual observed was using its time to move and call more than it was to feed. This has to do with the time of year - early spring - which in many passeriformes is a time for establishing beginning to attract mates and establish dominance hierarchies and breeding territories. Perhaps this Brown Creeper was starting to allocate more energy towards these activities, while still needing to feed enough to fuel its metabolism and begin to build stores for the energetically expensive business of mating that is soon to come. I will also note that at this point in the season, many of the most easily available overwintering insects and spiders found in tree bark may have been consumed, while the emergence of insects from their overwintering stage has likely yet to begin. So this is in all likelihood a time of some scarcity for the Brown Creeper - its frequent movement and its somewhat unfocused feeding may simply have been a reflection of food scarcity.

Two different plumages I observed were that of the Brown Creeper and the male Northern Cardinal. The brown creeper has a mottled brown and black pattern on its back. When it moves up the bark of a tree, it blends in so effectively that you can't even see it unless it's moving. This plumage is highly adaptive as a form of camouflage in the bird's feeding environment. It's also hard not to notice the pure white of its belly, especially when it flies. Perhaps this white is flashy enough to serve as a signal of attractiveness, and its location on the belly makes sense in this case because it is only visible when the bird is in flight (i.e. not foraging, when it wants to remain invisible). This plumage contrasts sharply with that of the male Northern Cardinal, which is about as conspicuous as could be. The bright red of the cardinal's feathers must serve as a mating cue, and certainly makes no effort to hide. Instead, in the dead of winter when nature is purely in shades of black, white, and brown, this red stands out like a sore thumb and must be associated with an early breeding/mate attracting season. It requires carotenoids from winter berries to maintain, so it serves a double function in that it makes creative use of a well-preserved winter food resource to indicate relative fitness.

Posted by sam_blair sam_blair, March 23, 2019 19:46

Observations

Photos / Sounds

No photos or sounds

What

Mallard Anas platyrhynchos

Observer

sam_blair

Date

March 23, 2019 02:00 PM EDT

Description

5 pairs at retention pond

Photos / Sounds

No photos or sounds

What

Canada Goose Branta canadensis

Observer

sam_blair

Date

March 23, 2019 02:00 PM EDT

Description

1 pair at retention pond

Photos / Sounds

No photos or sounds

What

Northern Cardinal Cardinalis cardinalis

Observer

sam_blair

Date

March 23, 2019 02:00 PM EDT

Description

At least two males seen, more heard, at retention pond

Photos / Sounds

No photos or sounds

What

American Robin Turdus migratorius

Observer

sam_blair

Date

March 23, 2019 02:00 PM EDT

Description

Many robins seen in trees around retention pond

Photos / Sounds

No photos or sounds

What

Black-capped Chickadee Poecile atricapillus

Observer

sam_blair

Date

March 23, 2019 02:00 PM EDT

Description

Flock of at least 4x individuals seen and heard in mature pines

Photos / Sounds

No photos or sounds

What

White-breasted Nuthatch Sitta carolinensis

Observer

sam_blair

Date

March 23, 2019 02:00 PM EDT

Description

1x individual seen and heard midway up a large pine

Photos / Sounds

No photos or sounds

What

American Brown Creeper Certhia americana

Observer

sam_blair

Date

March 23, 2019 02:00 PM EDT

Description

1x individual seen and heard moving among young and mature deciduous and coniferous trees, feeding.

Photos / Sounds

No photos or sounds

What

Pileated Woodpecker Dryocopus pileatus

Observer

sam_blair

Date

March 23, 2019 02:00 PM EDT

Description

Heard drumming nearby in stand of large white pines.

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