A key component to bird studies is bird banding, in which each bird has a band with a unique number placed on the bird. Sometimes, larger birds will also have colored bands placed on them which allows the individual to be recognized without recapturing them. This allows changes in populations, dispersal, survival and migratory movements to be studied. Banding birds also gives insight into natural history, particularly, on body conditions during taxing periods of their life cycle like breeding and migration. As part of my undergraduate studies, my class did an activity on bird banding at my professor’s house. Since he is a master bander we were able to sample birds in mist nets.
The study was conducted on November 21st, 2013 at Dr. Beaudry’s house in Alfred, New York from 9:15 am to 11:00 am. Mist nets (which are large thin nets that birds can’t see in flight and therefore fly into and get caught) were set up near feeders and the collected birds had data recorded about their body and they were banded and released. Data collected included age, sex, wing length, weight, and furcular fat score.
In total there were 16 birds captured from 4 species; Black-capped Chickadee (Poecile atricapillus), White-breasted Nuthatch (Sitta carolinensis), American Goldfinch (Carduelis tristis), and Purple Finch (Haemorhous purpureus). The details of each individual are recorded below (table 1).
Table 1. Birds collected from mist netting in Alfred, New York, USA on November 21st, 2013.
|Species||Status||Age||Sex||Number of individuals|
|Black-capped Chickadee||New||1+ years||Unknown||1|
|Black-capped Chickadee||New||<1 year||Unknown||5|
|Black-capped Chickadee||Recapture||1+ years||Unknown||1|
|White-breasted Nuthatch||New||1+ years||Male||1|
|White-breasted Nuthatch||Recapture||1+ years||Female||1|
|American Goldfinch||New||1+ years||Male||1|
|American Goldfinch||New||1+ years||Female||1|
|American Goldfinch||New||<1 year||Unknown||1|
The recaptured Black-capped Chickadee was originally banded at the study location in December 2011, and recaptured last year in November at the study location as well. Details about the recaptured White-breasted Nuthatch are currently unknown. The ratio of adults to juveniles in Black-capped Chickadee was 1:3, while in American Goldfinches it was 2:1 (table 1).
Purple Finch and American Goldfinch are both species that migrate in the winter time in general. However, there is a portion of their winter and summer ranges that overlaps, where they will live year round. Black-capped Chickadee and White-breasted Nuthatch do not migrate. In winter all 4 species exhibit a behavior known as winter flocking (Cornell Lab of Ornithology 2013). There are many benefits of flocking. These brightly colored birds are more exposed in winter and therefore easier for predators to capturing. Flocking means that predators are less likely to capture one as more birds are on the lookout for them. Food gathering efficiency is also increased by flocking behavior. In addition, there is reduced inter-species aggression which reduces competition (Barash 1974). Certain species such as Purple Finch and White-breasted Nuthatch that are normally territorial and aggressive during the rest of the year become docile in the winter months (Cornell Lab of Ornithology 2013).
The ratio of adults to juveniles in Black-capped Chickadee was 1:3, while in American Goldfinches it was 2:1 (table 1). From this ratio, we can deduce factors about the population such as juvenile morality, recruitment, and dispersion. If we can compare these ratios over time and at a number of locations we can gain more accurate information about the populations.
If we compare the number of juveniles we can estimate how many will survive/not emigrate before they become adults. In Black-capped Chickadee we can assume that 2 out of every 3 juveniles will either die or disperse to a new location. In American Goldfinches we can assume that juveniles are migrating to the study area, which explains why there is a higher number of adults than juveniles. This is known as Recruitment which is the process by which young birds are added to the breeding population (Robertson 2008).
Our sample is hardly qualified to characterize all birds of the species captured, or even the local populations in our area. Our sample was not representative. The first issue was the use of feeders. Some birds are not attracted to them and therefore they would not be captured. To control for this mist nests should be set up at locales where all birds would be or multiple nets could be set up in a variety of habitats. In addition time of day is a curtail part of this study. Most birds are active in the early morning and at dusk, not a 9 a.m., therefore, we must control for this. Sampling should be done at the times in which they are more active. This is because we will capture more and the bigger your sample the more likely it is to include rare species.
There was valuable information gained from this study however. If recaptured we can learn a great deal about the population birds in the area and most migration if they are seen in other locations. The data collected goes to a national group that will utilize it to understand populations of birds at a greater scale. We also know the common wintering species, and an estimate of their abundance. If monitored closer we can gain an even greater understanding of the local population.
Barash, D. P. 1974. An Advantage of Winter Flocking in the Black-Capped Chickadee, Parus Atricapillus. Ecology 55: 674-676.
Cornell Lab of Ornithology. 2013. Bird Guide: Black-capped Chickadee. Cornell University. Ithaca, New York, USA
Cornell Lab of Ornithology. 2013. Bird Guide: White-breasted Nuthatch. Cornell University. Ithaca, New York, USA
Cornell Lab of Ornithology. 2013. Bird Guide: American Goldfinch. Cornell University. Ithaca, New York, USA
Cornell Lab of Ornithology. 2013. Bird Guide: Purple Finch. Cornell University. Ithaca, New York, USA
ENVS240. 2013. Laboratory Handout: Lab #6: Mist-netting and passerine bird banding. Alfred University, Alfred, New York, USA.
Robertson, G. 2008. Using Winter Juvenile/Adult Ratios as Indices of Recruitment in Population Models. Waterbirds 31:152-158.