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Bird Diversity at the Morgan Arboretum

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.

Figure 1. Snow Buntings forage for food in our study site, the Morgan Arboretum.

Figure 1. Snow Buntings forage for food in our study site, the Morgan Arboretum.

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.

Figure 2. A Barred Owl rests in a conifer at the Arboretum. This species enjoys coniferous and deciduous woods.

Figure 2. A Barred Owl rests in a conifer at the Arboretum. This species enjoys coniferous and deciduous woods.

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.

Figure 3. The two main forest types. Left: A stand of coniferous trees. Right: Deciduous forest

Figure 3. The two main forest types. Left: A stand of coniferous trees. Right: Deciduous forest

Importance

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).

Figure 4. A Blue Jay eyes the photographer before moving on its way in coniferous forest.

Figure 4. A Blue Jay eyes the photographer before moving on its way in coniferous forest.

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).

Figure 5. In coniferous, a Black-capped Chickadee looks for its next perch.

Figure 5. In coniferous, a Black-capped Chickadee looks for its next perch.

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).

 Figure 6. White-breasted Nuthatches move down trees looking for insects

Figure 6. White-breasted Nuthatches move down trees looking for insects

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).

Birds Figure 7

Figure 7. A Downy Woodpecker examines a tree by pecking at the bark

Methods

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.

Figure 8. Map of areas used in Morgan Arboretum. C = coniferous  D = deciduous

Figure 8. Map of areas used in Morgan Arboretum. C = coniferous D = deciduous

References

(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,
42
: 594-598.

(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:

 http://lenichoir.org/

http://www.ace-eco.org/

http://www.the-scientist.com/?articles.view/articleNo/40967/title/Bird-Diversity-Drops-From-Forests-to-Farms/

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About Crystal Ernst

Hakai Institute postdoctoral scholar at Simon Fraser University (B.C.)

11 comments on “Bird Diversity at the Morgan Arboretum

  1. Nice post! And lovely photos, etc. as well. I wonder, however, about the ‘edge effects’ that may be quite common at the Arboretum – to what degree to you think the proximity of trails to your study areas could affect the results? Are any species particularly ‘edge-dwelling’? I think it would be important to think about this a little bit, and the ways your results could be influenced by the proxmity of the sites to trails.

    regardless, I enjoyed the post, and look forward to seeing the results from you data analysis!

    • Thanks for the feedback!
      While formulating our research question and methods we did consider this issue, as trails and human activity may have had an effect on bird where-abouts. In order to try to keep this issue at a minimum and so all replicates can be compared equally, we ensured that most of our plots were approximately similar distances to a trail. However, we will be looking forward to analyzing our data to see whether or not the trails did in fact have an effect on the presence of particular birds.
      Great points!

  2. Great post, it got me thinking though – how homogeneous are your woodland types? Are each of the coniferous blocks similar to one another in terms of the tree species they contain?

    • Thanks for the comment!
      Yes, we did take this into account. We used the tree species map of the Morgan Arboretum to keep the trees of each deciduous and coniferous stand as constant as possible. For our deciduous plots, trees were mainly Sugar Maple, Hickory, Ash, Oak and Red Maple (section 10). For our coniferous plots, two out of three were of red pine (section 27), but due to a lack of space the third was mainly white spruce (section 24) .Your feedback is much appreciated!

  3. Thank you for your insights!
    It is true, our site selection was very limited due to how few coniferous areas there are in the Arboretum. We believe most of our coniferous study areas were in fact plantations and if we had more time we would most definitely have been interested in studying how the natural and planted regions differed (sadly, that will have to be a research question for another day).
    Our map shows our six study areas (the big black and white squares) and all other numbers follow a legend (not depicted) describing the main vegetation types.
    Thank you for the advice, the tips and the link! We appreciate your feedback!

  4. I love your post! Very beautiful pictures and interesting facts that I never knew.

    How do you feel the time frame of your research project affected the diversity in both regions? Do you think the diversity would have changed if your research project was conducted earlier in the year?

    • Thank you for your comment!
      We felt kind of restricted in our data collection in the sense that we could only visit the Arboretum in the Fall season. It’s a transition season for the birds, and many of them had already begun their migration when we started our research. If our project could have been done earlier in the year, such as in the Spring or Summer, we feel that we could have seen many more birds and bird species, increasing the diversity.

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