Where Do Canadian Ferruginous Hawks Winter?

Catch up on the latest migration routes and wintering locations of Ferruginous Hawks! Read the full story in a recent Hawkwatch International blog post from University of Alberta M.Sc. student and Hawkwatch International Research Biologist Jesse Watson.

Adult male Ferruginous Hawk wearing a transmitter. Photo by Jesse Watson

Fall migration paths for 16 adult male Ferruginous Hawks from southern Canada

New paper on detectability of boreal birds during roadside and forested point counts

Read about Ph.D. Candidate Dan Yip’s recently published work below, and find the full article here

Sampling design schematic for our experiments near Calling Lake, Alberta, Canada, July 22–August 24, 2014. Wildlife Acoustics SM2 recorders were placed on the forest edge (1) and on the road (2), and playbacks were conducted to both recorders simultaneously along a transect following the forest edge. For forest playbacks, recorders were placed within the interior forest (3) and playback transects ran perpendicular to the road. 2014.


Point counts are one of the most common ways of collecting data to determine the relative abundance of birds. Many studies and monitoring programs, including the North American Breeding Bird Survey, use relative differences in counts of birds to assess changes in abundance over time and space. Many factors influence whether relative differences in counts of birds between various environmental conditions are reflective of actual differences in bird density. A major assumption of relative abundance is that birds with different song frequencies and amplitudes are heard at the same distances in different environmental conditions. We compared sound transmission in forest habitats and along low-use forestry roads, and calculated detection radius for different species to test the assumption that differences in bird counts between forest interior and roadside locations reflect actual differences in bird abundance. A playback–recording experiment was used to broadcast sounds through forest interior, along a forest edge, and down forestry roads in conifer and deciduous forests to determine whether sound propagation differed across environments. Sound attenuated significantly faster in forests than along roads or forest edges. Similarly, the distance at which bird songs could be detected was significantly shorter in forest than along the road or forest edge for 20 of 25 species. We found the area surveyed to be up to twice as large on road compared to within forests, which suggests that roadside surveys might inflate avian density estimates in comparison to off-road counts. Local atmospheric conditions also influenced detection probability, but the magnitude of the effect was weaker than the land-cover effect. Major differences in detection between roads and interior forest suggest that comparisons of surveys conducted along roadsides and in forest areas should be done carefully if the goal is to make direct comparisons of abundance.

Influence of minimum frequency on effective detection distance (EDR, with 95% confidence intervals) for each (A) species and (B) tone along different transects (edge, forest, and road) near Calling Lake, Alberta, Canada, July 22– August 24, 2014. ​

Using playback of territorial calls to investigate mechanisms of kin discrimination in red squirrels

A little while back, I did a Master’s degree at the University of Guelph with Prof. Andrew McAdam. I worked on the Kluane Red Squirrel Project, a collaborative project between several universities in Canada and the U.S. This long-term project was started nearly 30 years ago by Prof. Stan Boutin at the University of Alberta. The project has involved many undergraduate, graduates, and post-docs over the years studying a variety of ecological and evolutionary questions on a population of red squirrels in Kluane, Yukon.

  • A red squirrel in Kluane, Yukon, one of the individuals in the study population.

For my Master’s project, I was interested in red squirrel territorial behavior and the vocalizations, known as rattles, used to defend their territories. Red squirrel rattles are individually unique and have been shown to be used to discriminate kin, though the mechanism underlying this ability is unknown. In a recently published paper in Behavioral Ecology, I sought to distinguish between the mechanisms of ‘prior association’, where animals learn the phenotypes of kin they associate with early in life, and ‘phenotype matching’, where animals use a template to match phenotypes, thereby allowing them to recognize kin without an association early in life. I recorded rattles from squirrels in the field, and used those recordings in playback trials to measure the behavioural responses of squirrels to rattles from familiar kin, unfamiliar kin, and non-kin. One of the major benefits of the Kluane Red Squirrel project is that there is pedigree information for each squirrel, which means that we know who their mother and father is and who their siblings are. Without this information, this project would not have been possible, and full pedigree information is difficult to obtain for wild populations of animals.

  • Recording rattles from squirrels in the field to use in the playback trials

For red squirrels, familiar kin consisted of pair of squirrels that shared a natal nest (e.g. mother-offspring pairs and siblings from the same litter), and unfamiliar kin consisted of pairs of squirrels that did not share a natal nest (e.g. father-offspring pairs, siblings from different litters). Initial analyses revealed that red squirrels did not discriminate between familiar and unfamiliar kin, but also did not discriminate between kin and non-kin, despite previous evidence indicating this capability. Post-hoc analyses showed that a squirrel’s propensity to rattle in response to playback depended on an interaction between relatedness and how the playback stimuli had been recorded. Rattles used as the playback stimuli were either recorded from squirrels as they moved freely around their territories (unsolicited), or from squirrels as they were released from a trap or in response to a broadcast rattle (provoked). Red squirrels discriminated between rattles from close kin (relatedness coefficient of at least 0.5) and rattles from less related kin or non-kin (relatedness coefficient of less than 0.5) when the rattles were recorded from provoked squirrels. Squirrels did not exhibit kin discrimination in response to rattles that had been recorded from unprovoked squirrels.

This figure show the probability of a rattle response from the subject squirrel during the playback period by relatedness coefficient calculated from the pedigree and the collection method of obtaining the rattle stimulus. Unsolicited rattles were recorded from squirrels moving freely around their territories (n = 67 trials), and provoked rattles (n = 38 trials) were recorded from squirrels as they emerged from a live-trap or from squirrels responding to a rattle playback

This is potentially quite interesting, but it is important to note that this relationship was identified through exploratory post hoc analyses and needs to be tested more rigorously. If these results are robust, however, they would suggest that a squirrel’s physiological state might influence the structure of its rattles, including those individually distinctive structural features that are presumably used in discrimination. This raises interesting questions about what kind of information may be contained in the rattles and suggests that rattles may reflect the current state of stress or aggressiveness of the squirrel.

Photos and post by Julia Shonfield

Julia Shonfield, Jamieson C. Gorrell, David W. Coltman, Stan Boutin, Murray M. Humphries, David R. Wilson, Andrew G. McAdam. 2016. Using playback of territorial calls to investigate mechanisms of kin discrimination in red squirrels. Behavioral Ecology arw165. doi: 10.1093/beheco/arw165.

The abstract and a link to the full text can be found here:

If you are unable to access the article but are interested in reading it, you can email me at julia.shonfield@gmail.com and I can provide you with a copy.





The role of urban scavengers in estimating the number of birds killed by window collisions

Most people can remember an instance where a bird collided with one of the windows of their home. Most people don’t know is that this has been identified as one of the largest human-related causes of bird deaths in Canada. Many studies have attempted to estimate the exact number of mortalities however, instead of coming up with an accurate number, multiple biases have been identified. The largest of which being the removal of a dead bird from below a window by a scavenger before it can be recorded.

-A house cat drags a bird carcass away from a window where it had collided

The number of birds being removed by scavengers has been accounted for in previous estimates, however these previous scavenger studies have all taken place at wind turbines. There have been few carcass removal studies done in an urban environment and none of these have been used to determine a correction factor that can be used in determining a more accurate window collision estimate.

To learn more about the role scavengers play in an urban environment we conducted a carcass removal study at houses within Edmonton throughout 2015. The premise was simple: a dead bird and a time-lapse camera were placed below a window in the front yard of each house. After 1 week we returned to see if the carcass had been removed.

In the end 67.5% of carcasses were removed within 1 week, with the average time to removal being 3.46 days. The most common scavengers were Black-billed Magpies (61.6% of removals) and domestic or feral cats (16.1% of removals). There were also removals by American Crows, Blue Jays and Red squirrels.

-Black-billed magpies and squirrels were some of the scavengers responsible for removing bird carcasses from collision sites

Carcasses were less likely to be removed in the winter and the relative probability of a carcass removal was 7.6 times higher during mid-summer compared to mid-winter. Newer houses experienced a lower probability of removal compared to houses built before 1970. As well, developed neighbourhoods saw a lower probability of removal than undeveloped ones. These factors are similar to those factors we had previously identified as having a large effect on the likelihood of a bird-window collision suggesting those homes experiencing a larger number of collisions are also experiencing a higher number of scavenging events.

From these results, we came up with a correction factor for carcass removal by scavengers. 31.8% of carcasses were removed in the first 24 hours, which results in a 1.47 carcass removal rate. This means the number of carcasses detected in the first 24 hours needs to be adjusted by 1.47 to account for removal by scavengers. This rate is lower than the one developed from wind turbine studies that was used in creating the current estimate of bird-window collision mortality in Canada.

Using this removal rate and the citizen science data previously collected by the Birds and Windows project we estimated 957,440 (± 59,280 SD) birds are killed from window collisions at houses in Alberta each year. This is the most detailed estimate of bird-window collision fatalities in Canada as it’s based on the most detailed window collision study at houses to date and a carcass removal study located in the same area. Unlike previous studies, we did not extrapolate our results across the country. Our estimate is for Alberta, the area from which the data was collected. If we are to improve the current bird-window collision mortality estimate for Canada, more localized studies like ours are needed. Completing studies in each of the provinces will help reduce several of the existing biases in the fatality estimate at houses.

-Post and photos by Justine Kummer

Link to full text: http://www.ace-eco.org/vol11/iss2/art12/

Kummer, J. A., C. J. Nordell, T. M. Berry, C. V. Collins, C. R. L. Tse, and E. M. Bayne. 2016. Use of bird carcass removals by urban scavengers to adjust bird-window collision estimates. Avian Conservation and Ecology 11(2):12.

Thesis Defence Seminar on Red Squirrels

As part of her PhD thesis defense, Wild49 member Jessica Haines will be presenting a one-hour public seminar at 1pm on January 12, 2017, in room CCIS 1-243 at the University of Alberta. Her talk title and abstract are below.

Resources and Reproductive Trade-offs Affect Fitness, Life History Traits, and Sexual Selection in Red Squirrels
Animals face trade-offs throughout life between competing functions, such as between self-maintenance, reproduction, and survival. Resource allocation between these competing functions leads to different patterns of life history traits, changes in investment in reproductive effort, and different patterns of reproductive success. Reproductive investment is also influenced by the environment, for example by resource availability or mating opportunities. In this thesis, I test for evidence of reproductive and life history trade-offs, as well as for whether individual- and population-level resource availability affect reproduction and life history traits. I first tested whether there was evidence of age-related changes in reproductive success in male red squirrels, and in particular whether there was evidence of senescent decline in older ages. I also considered whether there was a trade-off between early-life reproduction and late-life senescence in male red squirrels. Next, I tested whether encountering a resource pulse affected life history traits. I also explored whether life history trade-offs and the fitness consequences of life history traits were affected by encountering a resource pulse called a mast year. Finally, I tested whether individual-level food availability was related with breeding season timing and reproductive success in male and female red squirrels.