Research Proposal: Observational Study

Angry : A Study of Avian Inter- Domination at a Winter Feeding Site

Sean Holt

Introduction

In North America, in lower elevations, many people are likely to see Dark-Eyed Juncos (Junco hyemalis) that migrate to lower elevations from their high-altitude breeding grounds. Juncos are migratory birds that travel from higher elevations in the summer to lower elevations where food is more plentiful in the winter. There are as many as eight different sub-species of Dark-eyed Junco (Junco hyemalis) and

Yellow-eyed Junco (Junco phaeonotus) in North America and as many as five here in Colorado. This includes the Oregon Junco (J. h. oreganus), the Pink-sided Junco (J. h. mearnsi), the White-winged Junco

(J. h. aikeni), the Grey-headed Junco (J. h. caniceps), and the Slate-colored Junco (J. h. hyemalis). These birds are notorious for being competitive and establish a hierarchy within flocks (Strokes & Strokes,

2006; Sabine, 1959), which makes them common test subjects for behavioral studies.

Many experiments have been geared toward explaining what makes one junco more dominant than another (Cristol et al. 1992; Cristol et al. 1990), while some have been geared toward seeing which sub-species is more dominant than another (Burns, 2009; Wiedenmann et al. 1987). Cristol et al. 1992 examined minor color differences between birds to see whether they affected the dominance of birds from different flocks. Their study used an indoor aviary to contain these birds and keep track of individuals, much like other studies (Cristol et al. 1990; Vézina et al. 1999; Wiedenmann et al. 1987). Researchers attached colored bands to the right legs of the birds and scored the birds’ dominance on a "win-loss" system. A junco that gave way to a approaching it was recorded as a "loss", while the bird that approached it was given a "win" because it was able to gain access to a branch or a piece of food. This scoring system was used in Cristol et al. (1990), Millikan et al. (1985), and Wiedenmann et al. (1987).

Cristol found no significant difference between the different colored bands, using an averaging system called dominance scoring (found by dividing the number of wins by the total number of confrontations with other birds) where the baseline is .500. The study concluded that while large plumage coloration might make a difference between dominance scores, minor color differences, in this case the colored bands, didn't make a significant difference. However, different species and sub-species have many different traits that could contribute to higher dominance scores. Size, sex, coloration, and age all contribute to an individual junco’s higher dominance (Millikan et al. 1985; Burns, 2009; Vézina et al.

1999; Wiedenmann et al. 1987; Cristol et al. 1990). Another interesting characteristic about junco dominance is that, in most cases, it is a triangular dominance (Strokes & Strokes, 2006). Triangular dominance occurs when bird A is dominant over bird B, bird B is dominant over bird C and bird C is dominant over bird A (A>B, B>C, C>A). In some flocks, however, there is a bird that dominates all other birds and there is another bird that is dominated by all other birds (Wiedenmann et al. 1987).

For my study, I will be testing the hypothesis that larger, more brightly colored sub-species of juncos are more dominant than smaller, less brightly colored varieties of juncos. My aim is to observe the different sub-species to determine if size and plumage color affect behaviors, particularly in relation to their dominance scores. I will also be observing the junco's aggressive encounters towards other wintering birds seen at the feeding site. Most of the birds that are likely to be observed are the House Finch

(Carpodacus mexicanus), the House Sparrow (Passer domesticus), the Harris Sparrow (Zonotrichia querula), the American Tree Sparrow (Spizella arborea), and the Song Sparrow (Melospiza melodia).

Methods

I will observe juncos and other species in an outdoor study site, viewing the birds from a room through a large window. Outside of the window, I will scatter bird seed on the ground and in an above ground feeding box. In this site, there are a few medium-sized native bushes that have already lost all of their leaves. Each day, 580 grams of mixed seeds that consist of Proso Millet (Panicum miliaceum) and

Black Sunflower Seeds (Helianthus) will be added to the site.

This study site hopefully will be visited by all of the sub-species and other wintering bird species in Colorado in order to gain a sample size of at least 50 to 75 dominance encounters between sub-species. To observe all of the birds, I will set up a video camera overlooking the site. This will enable me to make sure that I can see all of the bird-to-bird dominance displays that occur. Due to the fact that I am conducting this study specifically to observe how the different species interact with each other, any birds that display dominance over another bird from the same species or sub-species will not be recorded

(example: J. h. mearnsi v. J. h. mearnsi).

I will record the dominance patterns using two different systems. First, will be the common “win- loss” system. This is where a junco pecks or approaches a few centimeters toward another junco. I will record a “win” for the junco that caused the other junco to retreat and a “loss” for the junco that retreated.

However, the second system is slightly different. This system includes three different outcomes of an aggressive encounter: active displacement, where one junco actively displaces another junco; passive displacement, where one junco’s presence drives away another junco; and a standoff, where neither junco is displaced by an aggressive encounter.

Statistical Analysis: I will be using a one-way analysis of variance (ANOVA) to determine the statistical significance between the dominance scores of the five different sub-species of junco and the other five different wintering birds included. In this test α=0.05 is the null hypothesis rejection level. I will also be comparing the data of different sub-species of junco and other species by means of the chi squared test

(χ2) (Ex. Junco hyemalis mearnsi v. Spizella arborea).

Alternatives and Impacts

Since this study is purely observational, the use of vertebrate is justified in order to determine which sub-species is dominant to another and for what reasons. I will be having two professional ornithologists on site supervising my study. Since these are wild animals, there will be no inclusion of overnight housing or confinement to a specific area. The birds are free to fly away and not come back after a visit to the study site. For all of the animals that will be used in my study, the sample size, sex, and age of the population are not pre-determined due to the fact that this is a wild animal study.

The seed that will be provided is called “Wild Thing!” and can be bought at a supermarket.

Literature Cited

Burns, C. B. 2009. The “white-winged” dark-eyed junco of the Black Hills. South Dakota Bird Notes 61:32-35.

Cristol, D. A., V. Nolan Jr., and E. D. Ketterson. 1990. Effect of prior residence on dominance status of dark-eyed juncos, Junco hyemalis. Animal Behaviour 40:580-586.

Cristol, D. A., C. S. Chiu, S. M. Peckham, et al. 1992. Color bands do not affect dominance status in captive flocks of wintering dark-eyed juncos. The Condor 94:537-539.

Millikan, G. C., P. Gaddis, and H. R. Pulliam. 1985. Interspecific dominance and the foraging behaviour of juncos. Animal Behaviour 33:428-435.

Sabine, W. S. 1959. The winter society of the Oregon junco: intolerance, dominance, and the pecking order. The Condor 61:110-135.

Stokes, L., and D. Stokes. 2006. Birds of a feather. Birder’s World 20:52-53.

Vezina, F. and D. W. Thomas. 2000. Social status does not affect resting metabolic rate in wintering dark- eyed junco (Junco hyemalis). Physiological and Biochemical Zoology 73:231-236.

Wiedenmann, R. N., and K. N. Rabenold. 1987. The effects of social dominance between two subspecies of dark-eyed juncos, Junco hyemalis. Animal Behaviour 35:856-864.