Burrowing Owl Lit Roundup

Burrowing Owls continue to fascinate photographers, birders, environmentalists, and scientists. Here’s a roundup of some recent (and some older) Burrowing Owl literature.

Burrowing Owls feature prominently among the “100 Greatest Owl Pictures You’ll Ever See.” The ad-laden array of charming, funny, and touching photos doesn’t identify the various included species, but readers will have little difficulty spotting our local favorite owl variety. Thanks to Richard Healey for sharing the link.

Urbanizing owls in Marco Island, Florida

Burrowing Owls are in trouble in Florida. They had been numerous in the state but development has destroyed their wilderness habitats. Now the city council of Marco Island has started paying homeowners $250 a year to allow Burrowing Owls to live in their yards. Check it out! Trained volunteers install artificial burrows, and in many cases the owls move in. The owls there have become fairly urbanized, living in much closer proximity to people than owls in the countryside. Thanks to Susanna Deiss Chivian for sharing this item.

The distinction between urban and rural owls is for real, and individual owls also differ in personality traits such as tolerance for humans. That’s among the findings of a research report in Nature magazine, titled “Personality-dependent breeding dispersal in rural but not urban burrowing owls.” Authors Alvaro Luna and associates studied hundreds of owls in and around the city of Bahia Blanca in Argentina. They write, “Urban owls … excavate their nests in small private and public gardens in urbanised residential areas, unbuilt spaces among houses, curbs of streets and large avenues, and are in constant contact with homeowners, children, pedestrians and intense car traffic.” My own observations in the park last year confirm the personality distinction. Some owls seem unbothered by humans even in close proximity. Others take flight when a human gets within 50 feet of them.

Burrowing Owls are capable of adapting to expanding urban environments, report the authors of another study done in Argentina, where the birds are well established in urban areas. “Burrowing owl nest distribution and density in relation to urban development” in the Ethology, Ecology and Evolution journal reports on a study in two rapidly expanding small towns, and finds that Burrowing Owl nesting sites in both places increased.

Burrowing Owls historically have been ecologically flexible, living in a wide range of habitats and climates. Researchers Meena Madan and associates draw this conclusion from a study published in Palaeontologia Electronica of Burrowing Owl fossils recovered from the La Brea tarpits, Los Angeles, during a glacial period 20-18,000 years ago. Contrary to expectations based on Bergman’s rule, which holds that animals in cold climates grow larger and with heavier bones than in warm climates, the Burrowing Owls showed no anatomical changes during the glacial period.

A pair of Burrowing Owls were discovered breeding in North Central Oklahoma, the first seen there since the 1960s. The species was once widespread in the state, but habitat conversion from grasslands to agriculture and the destruction of prairie dog towns crashed the owl population in the following decades. The report is in the Oklahoma Ornithological Society journal.

Differences between the Western Burrowing Owl (Athene cunicularia hypugaea) and the Florida Burrowing Owl (A.c. floridana) are explored on the birdfinding.info website, which features numerous photos of the Florida variety with estimates of its surviving range.

Cover of 2003 US Fish and Wildlife Service Report

A comprehensive study of the Western Burrowing Owl was published by the U.S. Fish and Wildlife Service in 2003. The book, titled “Status Assessment and Conservation Plan for the Western Burrowing Owl in the United States — Biological Technical Publication” has eight authors, 120 pages and includes 19 figures, 11 tables, and detailed material from 24 states. It’s available free online here. A little dated — compare the 2007 volume reviewed here — but a must-read volume for owl aficionados. Note that almost all of it deals with the owls in their rural breeding habitats. “Little information exists on migration routes and times,”and there is “little information regarding wintering areas” (p. 7) ; and again, “Little is known about wintering habitat requirements” (p. 12) and “very little is known about habitats used during the winter” (p. 27). Thus the book is not directly instructive regarding the owls we see in the park; they are not breeding here but wintering. The report finds that an area of at least 35 hectares (86.5 acres) is needed for Burrowing Owls to nest and breed (p. 26). If that’s true, almost all of Cesar Chavez Park (90 acres) would have to be protected to establish a breeding colony here. The book makes no mention of urbanized owls such as those observed in Florida and Argentina.

Owl Flying
Photos copyright City of San Jose, from Bay Nature 1/30/15

One of the few remaining Bay Area breeding sites is in a fenced 180-acre facility surrounding the wastewater treatment facility of the City of San Jose. The area, not open to the public, is owned by the City and managed by the local Audubon Society on a City grant. Freelance writer Laura Hautala visited there and published an engaging, readable report in the excellent Bay Nature magazine a few years ago. Thanks to Sheila Jordan for spotting and sharing this article.

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