Sunday, July 14, 2013

Reverse migration....aka my thesis!

Well after almost 2 years working towards my Master's and another year before that for my undergrad thesis I have finally finished my thesis on reverse migration!

Brandon has done a nice photo essay capturing reverse migrants with his photography, so check out his blog for more pics.

I've pasted my abstract below for your enjoyment....

*********************************************************************************** Abstract
The spring reverse migration of songbirds (i.e., birds flying in the direction opposite to be expected), within the Great Lakes region is controversial because it is not understood if the extent or reversal of flight direction in spring is truly a change in migratory patterns or a brief anomaly. It is also not clear what the fitness and community level impacts are. My objective was to determine what and how weather influences reverse migration and to determine which species and families of birds participate the most frequently in this form of flight. I examined species which are participatory (and those that are not) as well as the impacts of specific weather covariates on the abundance of songbirds and focused on the putative reverse migration of passerines.

Field sites were located at the extreme southern tip of Fish Point, Pelee Island (2010-2012) and Point Pelee National Park (2012), where my field assistant and I visually recorded the total number of birds observed to be reverse migrating, while identifying all birds to species or family as best possible. This study was conducted over 97 days during April 26 – May 20, in 2010-2012. Information pertaining to potential reverse migration has only been formally documented twice in the Great Lakes region, most recently in 1951.

I undertook a descriptive analysis to compare the numbers of individuals of bird species and families. Temperate and neotropical migrants were examined, compared and divided into sub-sets based on their geographic ranges. I identified species at risk which I observed during reverse migrations as well as vagrants. Based on provincial population estimates, I determined the proportion of all reverse migrants where ≥200 individuals were observed. A descriptive analysis was undertaken to determine differences between sites (i.e., Point Pelee and Fish Point) in the final year of surveys (2012). Species and abundance were comparatively differentiated between each site location and subsequently compared.

A total of 61,677 birds of 80 species was documented. My results indicate temperate migrants vastly
outnumbered neotropical migrants (as much as 4:1) and numbers of birds varied between study sites. Temperate migrants were noted to be more common (in the final study year) at Point Pelee compared to Fish Point, while neotropical migrants were more numerous at Fish Point than Point Pelee. Despite most migrant species participating in reverse migrations (i.e., of the species regularly occurring in the Pelee region at this time of year), complete absences were noted most notably in Catharus thrushes, while species such as Rose-breasted Grosbeak, and Scarlet Tanager, and families such as Tyrant Flycatchers, Vireos and Sparrows were observed to be in less abundance than anticipated. Species at risk and vagrants were noted relatively frequently during this study, suggesting that these surveys are an efficient and important tool for migration monitoring in this region. Disproportionally diurnal migrants, most notably Blackbirds, were observed to engage in reverse migration in higher numbers than nocturnal migrants, such as Wood Warblers.

Seven weather covariates were measured and modeled with the total number of birds detected using R to
determine which covariates explain the most amount of variation of the total number of birds during my surveys. I used an AICc approach to select the best model for each hypothesis. After selecting the top weather covariates with time lags according to the best (lowest) AICc values, I built general models by comparing all possible combinations of the covariates identified in the top models for each hypothesis. I included a random effect intercept for study site to discern any site difference or correlations between Point Pelee and Fish Point and specified a Poisson distribution (log link function as implemented in the LMER package) due to the data set being continuous (time-series) and count oriented.

My adjusted time lag results show that most migrants tend to migrate during and ahead of inclement weather. I also found that all identified covariates influence reverse migration to some degree. Wind direction and barometric pressure were the most significant of the covariates examined (β = 0.718 and -0.213, respectively). Specifically, wind direction is the most important covariate in explaining reverse migration, with days of south winds dramatically increasing the probability of higher numbers of birds during surveys. Low barometric pressure is also important for explaining the number of observed reverse migrants; therefore days with lower barometric pressure have a greater likelihood of increased bird observations.

Based on my observations and results I theorized that while reverse migration pertains to a distinct form of flight, it is likely not an actual form of migration. This form of flight in its simplest is likely a form of re-orientation, whereby migratory passerines take advantage of local weather conditions by flying south extended distances. I anticipate this form of flight has serious repercussions on the fitness levels and life cycles of migratory passerines.

Studies looking at reverse migration provide a useful tool for migration monitoring, particularly on an underexplored phenomenon. Observations of thousands of birds, many of which are either species at risk or vagrants, in an efficient manner are vital for determining population trends related to migratory birds. Continuing this study will allow for a continual monitoring program to assess songbird populations passing through the lower Great Lakes region. Understanding the impacts of climate and climate change on migratory songbirds is another aspect this study will help to address in the future.

And for shits and giggles, I've put some of the pics I really like from Pelee Island....

Any guesses as to what species this is????? Hint: its rare! Copyright Graeme Gibson.

Blue-winged Warbler - Fish Point - May 2012, Copyright Brandon Holden.

male Dickcissel, Fish Point, May 3, 2012. Brandon Holden

male Golden-winged Warbler, Fish Point, May 3, 2012. Brandon Holden.

female Prothonotary Warbler, May 3, 2012. Brandon Holden.

Willets, Pelee Island, May 2012.

adult basic Laughing Gull, West Dock, July 2011.

Henslow's Sparrow, Sheridan's Point, May 6, 2011. Copyright Scott Hulme.

adult male Summer Tanager, Stone Road Alvar, April 28, 2011.

Likely one of my favourite pics of all time. If you don't know what this is, look it up! :)

male Canada Warbler, Fish Point, May 2011.

sunrise at Fish Point! :)
No post about Pelee Island would be complete without the picture of the Burrowing Owl Mike and I found in 2008!!!

Thursday, July 11, 2013

Random stuff from the spring

Snowy Egret, near Port Hope, late April 2013

Lark Sparrow, Erieau, April 26th

24 Willets, Pelee Island, April 28th

male Prothonotary Warbler, Fish Point, Pelee Island, mid-May 2013

Hudsonian Godwit, Rainy River (Harris Hill), May 22, 2013

Brewer's Blackbird, Harris Hill, May 22, 2013

Yellow-headed Blackbird, Harris Hill, Rainy River, May 24, 2013

Western Meadowlark, Rainy River, May 25, 2013
American Bittern, Point Pelee NP near the Sparrow Field, early May 2013

Blue Grosbeak (first-alternate male), Pelee Island, May 9, 2013

Laughing Gull, Point Pelee NP Tip, May 5(?), 2013

Monday, July 8, 2013

Breeding Bird Surveys

Well, its been a bit since I last posted....things have been happening! Work, aka breeding bird season, as well as working on school (more on that shortly) have been hectic!

On the Canada Day long-weekend, My Dad and I went on a whirlwind trip up to Cochrane, conducting 2 BBS routes for Environment Canada and Bird Studies Canada. BSC, in partnership with CWS has an incentive program running, where participants conducting BBS routes in northern Ontario can claim up to $400/500 per route, IF they are willing to do the route(s) for at least 3 years (3 years is needed to enable CWS to analyze/compare the data you collect)! For more information, check out BSC's link:

The BBS is a North American run (led by the US Geological Survey and the CWS), roadside survey, used for monitoring bird populations. BBS routes are 40km in length. Participants are required to stop every 800m, listening for 3 minutes at each point count, recording every bird they hear within 400m. Basically for a birder, as well as someone who does breeding bird work for consulting firms this is the ultimate 'test', so to speak in engaging your auditory bird skills! :)

I signed up for two this year and have already agreed to a 3rd route next year! Our routes were located about 100km east of Cochrane and the other centred around the town of Matachewan.

Both sites were really different, but interesting in the different species we encountered.

The Cochrane site (Kabika Lake), was what you'd think of for the far northern boreal stuff, picking up most of the boreal breeders: Connecticut Warbler, Boreal Chickadee, Olive-sided Flycatcher, Black-backed Woodpecker, Spruce Grouse, not too mention some surprising stuff like a E. Whip-poor Will and a Pine Warbler, both quite far north of their expected breeding ranges in northern Ontario.

To see a complete list of what we saw (cumulatively), click the link:

A pair of VERY territorial Great Yellowlegs, on the Kabika Lake BBS route, June 30, 2013.

After doing the Kabika Lake BBS, we headed back into Cochrane. The drive from Cochrane took a while, since we were in my Dad's Toyota Camry, we had to go slow, since the roads weren't too great (but not that bad for logging roads!). After lunch we headed towards Matachewan, almost 300km from Kabika Lake!

Getting into Matachewan we scouted the route, before grabbing a place to stay (we camped along the road at our Kabika Lake site).

The Matachewan route was really good too, being very different from Kabika Lake. Warblers seemed to be present in higher diversity (and numbers), but we still had some boreal species, like Black-backed Woodpecker, Lincoln's Sparrows, but we were also getting species you think of for Central Ontario, like Black-throated Blue Warbler and lots and lots of Veeries!

Alder Flycatchers are relatively common in northern Ontario, depending on habitat

Check out our ebird checklist for the route:

It was a pretty fun jaunt up north. We saw lots of birds, but also some cool total 5 Bears, and a short but sweet look at a Lynx, as well as good looks at a Wolf!