Part One: Introduction

The western screech owl (Megascops kennicottii) is a robin sized owl who packs quite a punch. Standing only 7 to 10 inches tall, this owl can still hold its own next to the much larger members of the owl (Strigidae) family. On occasion they can be seen taking down prey much larger than themselves, including cottontail rabbits and even mallards (The Cornell Lab of Ornithology). Although often hard to see because of its excellent camouflage this bird can be identified by its small stocky build, distinct ear tufts and yellow eye colour (COSEWIC). Brown, grey or rufous in colour with vertical stripes on its underbelly this owl blends in excellently with the bark on the trees in its habitat (The Cornell Lab of Ornithology).

This little guy can be found along the coast of North America and into the southern interior of British Columbia, including Kamloops. It’s territory extends through the coast and mountain valleys of the interior United States, reaching all the way to north western Mexico (The Cornell Lab of Ornithology).

The western screech owl is non migratory and remains in the same territory year round. It does not need to migrate due to its generalist nature. The western screech owl can feed from a large variety of sources including small mammals, insects, fish and even small birds. It is found in heavily forested areas where it nests and roosts in tree cavities (Campbell 2013).

The name “screech owl” is a misnomer for this bird whose call is more a series of toots in the pattern of a bouncing ball. “Screech” is better suited for the eastern screech owl, another member of the Megascops genus (The Cornell Lab of Ornithology).

Although the species as a whole is not considered “at risk”, local populations are threatened due to their habitat also being prime real estate for human populations. Deforestation as well as removal of dead trees by humans has significantly decreased the number of optimal nesting sights for western screech owls. This is seen in the decreasing population of the western screech owl in the metro Vancouver and Southern Vancouver Island areas which is thought to be due to the increasing development in these regions (COSEWIC).

A way you can help conservation efforts in these regions is to provide nesting boxes in your yard. An optimal nest box for these owls should be 10-30 feet off the ground, made of reclaimed wood and East or South facing. The entrance hole should be 3 inches in diameter, have a height of at least 14 inches and be 10 inches deep and 11 3/4 inches wide. More tips on building your own nest box can be found at https://nestwatch.org/learn/all-about-birdhouses/birds/western-screech-owl/.

A fact that I found particularly interesting about this bird is that after hatchlings leave after 28 days in the nest, both parents continue to care for their young for another 5-6 weeks (Audubon). This is likely because owlets cannot fly immediately after they leave the nest and therefore still need help when it comes to feeding and protection from predators. They gain the ability to fly and become independent at around 8-10 weeks after leaving the nest (Songbird Garden). All our lives we are taught of the “tough love” approach to parenting that birds have, of them pushing their young out of the nest, and only the strong survive. This is why I personally find parental care in these birds so interesting. However, after some research I have found parental care is not particularly unusual birds and is seen in many species (Cockburn 2006).

These raptors, tiny but mighty are an important species which deserve to be protected. Constant urbanization has become a threat to this beautiful bird, but there are still things that can be done to help the population flourish. On an individual level, providing nest boxes is an excellent way to help, however, more needs to be done on an industrial scale for the conservation of this species among many others. The consistent growth of human civilization is inevitable but I hope in the future it is done with more consideration and care for the species’ it impacts. With this I hope that western screech owls can be seen and enjoyed for generations to come.

Part Two: Dispersal of Juvenile Western Screech Owls

An area of interest for western screech owls is when, why and how they disperse. Specifically whether dominant or subordinate juveniles disperse first. There was an experiment done by Ellsworth and Belthoff to determine the correlation between dominance and dispersal time. western screech owls are a prime species to observe for this behaviour because of their use of nest boxes. The birds were observed from hatching and their dominance status was determined throughout their time in the nest. This was determined using a system of “wins and losses” whenever there was a physical contact between two fledglings that was considered aggressive. Although not overtly aggressive with each other, they did engage in a series of pecks, shoves and displacements. Using this system of wins and loses they create a scale of most to least dominant fledgling (Ellsworth and Belthoff).

Dispersal distances between the most dominant and most subordinate fledglings were compared. During the determination of the dominance rankings it was found that females were the most dominant in most of the broods observed, this is thought to be due to their larger body size. (Ellsworth and Belthoff 2015)

It was found that the most dominant fledglings dispersed first with the most subordinate dispersing about 2 months after the first fledgling. Interestingly, they often left in the order of dominance the researchers had determined. The researchers determined this to be because of dominant owlets developing faster and becoming independent sooner. Moreover, in broods with smaller clutch sizes it was found that the most subordinate fledgling left sooner on average than those in larger clutch sizes. This can be inferred to be because of a decrease in competition between brood mates, and therefore quicker development and independence (Ellsworth and Belthoff 2015). This experiment allows researchers to have a better understanding of why and when western screech owl fledglings disperse which can have huge impacts when it comes to rehabilitation and release of abandoned owlets. The more we know about their natural cycles, the better we can assist them and prepare them for life outside the nest.

References

Audubon: Guide to North American Birds (n.d). Retrieved October 20, 2019. https://www.audubon.org/field-guide/bird/western-screech-owl

Campbell, S. (2013, May 01). Western screech owl hit by car recovering at north island wildlife recovery centre. Alberni Valley Times Retrieved from: https://search-proquest-com.ezproxy.viu.ca/docview/1347736314?accountid=12246

Cockburn A. (2006). Prevalence of different modes of parental care in birds. Proceedings. Biological sciences, 273(1592), 1375–1383. Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1560291/?tool=pmcentrez&report=abstract

Committee on the Status of Endangered Wildlife in Canada: Assessment and Status Report on the Western Screech-Owl kennicottii subspecies Megascops kennicottii kennicottii and the Western Screech-Owl macfarlanei subspecies Megascops kennicottii macfarlanei in Canada (2012). Retrieved from https://www.sararegistry.gc.ca/virtual_sara/files/cosewic/sr_western_screech-owl_1012_e.pdf

Cornell Lab of Ornithology: All About Birds (n.d). Retrieved October 20, 2019. https://www.allaboutbirds.org/guide/Western_Screech-Owl/overview

Ellsworth E. A; Belthoff J.R. (1999). Effects of social status on the dispersal behaviour of juvenile western screech-owls. Animal Behaviour, 57(4), 883-892. Retrieved from: https://www-sciencedirect-com.ezproxy.viu.ca/science/article/pii/S0003347298910508

NestWatch: Where Birds Come to Life (n.d). Retrieved October 20, 2019. https://nestwatch.org/learn/all-about-birdhouses/birds/western-screech-owl/

Songbird Garden (n.d). Retrieved October 20, 2019. https://www.songbirdgarden.com/store/info/infoview.asp?documentid=183