Birds come in a wide variety of species, each with its own distinctive colours, calls and behaviours. While some birds’ lifestyles cause them to enter in direct competition with others, such as two species competing for the same nesting sites, other groups may avoid such conflicts by adapting to different food sources and habitats. In the Saint-Lawrence Lowlands, these habitats can be broken down into two main forest types: deciduous and coniferous. Between these two forest types, some bird populations may be more diverse than others. Therefore, through our research at the Morgan Arboretum, we wish to see if there is a correlation between forest type and bird diversity.
Diversity is the measurement of the abundance of individuals and the variety of species in an area. A place with more species in greater numbers has a higher diversity, and vice-versa. A less diverse area could have one species that is more common because it outcompetes other birds, and limits the total number of species encountered (1).
For our research, the relative abundance of various birds within each forest type will be noted and should tell us which forest has higher bird diversity. According to the study by MacArthur et al. 1961, birds may either prefer specific forest habitats (and live off of resources unique to that habitat) or they may all live in one large habitat and have specialized ways of living for specific situations (2). Birds showing preference for one type of forest will increase the diversity in that area, but some other bird species might be equally abundant in both places, causing neither forest to be more diverse than the other.
There are many reasons why one forest may attract more species than another. Factors such as vegetation and the physical structure of the trees may influence food sources and provide protection from predators and also the best nesting sites. These may contribute to a forest’s ability to attract more birds (1). For example, coniferous forests provide shelter in winter with their pine needles and their cones and seeds are present throughout the year, offering overwintering birds important food sources. On the other hand, deciduous forests provide more fruit variety during certain seasons, attracting greater numbers of birds.
A previous study by James and Rathbun in 1981 (3) showed that coniferous forests supported the lowest diversity of bird species, as did a later study in 1996 by Willson and Comet (4). The overall trend seems to show that deciduous stands support a greater amount of avian species.
The general public is often not aware of the importance of bird diversity. Birds, admired for their beauty and wonderful songs, are often welcomed in parks or backyards, as humans enjoy their wonderful spirit and magnificent colors. However, not only are they beautiful, they are also excellent environmental indicators. A habitat’s good health can be implied by the presence of birds (5). They help pollinate and disperse seeds and many naturalists refer to them as “agents of dispersal” (6). Additionally, birds control pest levels by the sheer number of insects and mice various species consume (6). For these reasons, having a high bird diversity in any given forest is important for the environment’s overall health, and studying bird diversity is a good way to gain knowledge of the forests that they live in (5).
Examples of Study Species
As we are looking at the overall bird diversity in each forest type, our study species will include every bird noted during our data collection. One of the most common birds seen are Blue Jays. This species often hangs around forest edges, and breeds in both coniferous and deciduous woods. They have distinctive blue, white and black plumage, and use a complex communication system with a large variety of calls (7).
The call of the Black-Capped Chickadee is as equally common. This songbird has a black cap and black bib, white cheeks and grey and white feathers covering its round body. They are found all around North America, but their preferred habitat is deciduous and mixed forests (7).
Another forest-loving species that we hoped to see is the White-breasted Nuthatch, a songbird with a black cap and back plumage of a grey-blue color. This bird is territorial and it is usually more abundant in deciduous forests than in coniferous ones (7).
It is probable that the most commonly seen woodpecker will be the Downy, which is the smallest woodpecker in North America. They have a relatively short bill compared to their body size, their plumage is black and white and the males have a small red patch on the back of their head. This woodpecker breeds mainly in deciduous forests (7).
We selected three replicates of deciduous forest and three of coniferous forest, each of 50mx50m, and at least 50m apart from each other. We split up in two teams, one for each type of forest, changing the people in each team and the order in which we visited the replicates to ensure the process was as unbiased as possible.
We spent 10 minutes of quiet time in each replicate during which we did not include the birds seen or heard in our data, then we spent 30 minutes bird watching. During these 30 minutes, every bird seen or heard within the range our our replicate was included in our data, but traces of birds (pellets, woodpecker holes, etc.) were not. Time of day and weather conditions were also logged.
(1) Gill, F. (1995) Ornithology (2nd ed.). New York: W. H. Freeman and Company.
Available from: http://www.jstor.org/stable/1932254
(2) MacArthur, R. & MacArthur, J. (1961). On bird species diversity. Ecology,
(3) James, F. & Rathbun, S. (1981). Rarefaction, relative abundance, and diversity of avian communities. The Auk, 98: 785-800. Available from: https://sora.unm.edu/sites/default/files/journals/auk/v098n04/p0785-p0800.pdf
(4) Willson, M. & Comet, T. (1996). Bird communities of northern forests: ecological correlates of diversity and abundance in the understory. The Condor, 98: 350-362. Available from: https://sora.unm.edu/sites/default/files/journals/condor/v098n02/p0350-p0362.pdf
(5) Birds as Indicators of Sustainability. Birds in Backyards. Web. http://www.birdsinbackyards.net/birds/Birds-Indicators-Sustainability
(6) The Importance of Birds. Iowa NatureMapping. Web. http://www.extension.iastate.edu/naturemapping/monitoring/importance_birds.htm
(7) Cornell Lab of Ornithology, Cornell University,
Web. http://www.birds.cornell.edu/Page.aspx?pid=1478 Nov. 06 2014.
Further Reading on Birds and Bird Diversity: