378 THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 123, No. 2, June 2011 
The Wilson Journal of Ornithology 123(2):378—381. 2011 
Breeding Dispersal of a Burrowing Owl from Arizona to Saskatchewan 
Geoffrey L. Holroyd , 1 Courtney J. Conway , 2 3 and Helen E. Trefry 1 
ABSTRACT.—We document a female Burrowing 
Owl (Athene cunicularia) that nested in Arizona and 
dispersed 1.860 km to Saskatchewan, where she 
successfully raised seven young during the same 
breeding season. The dispersal path between these two 
locations has not been documented previously. This is 
the longest distance ever recorded for breeding dispersal 
for any raptor within the same breeding season and 
possibly for any bird species. Received 24 Max 2010. 
Accepted 21 January 20/1. 
Dispersal has important implications for popu¬ 
lation biology and evolution (Greenwood 1980. 
Wiens 2001). Breeding dispersal has been defined 
as movement between two successive breeding 
areas or social groups (Clobert et al. 2001). 
Breeding dispersal in birds is typically used to 
refer to movements between 2 years (Greenwood 
1980. Greenwood and Harvey 1982). but within- 
year breeding dispersal can also occur when 
individuals move between two subsequent breed¬ 
ing attempts (Rosier et al. 2006). 
Renesting (defined by Fankhauser 1964) has 
been documented for numerous species after an 
initial nesting attempt fails (Newton 1979). 
Second nesting attempts (those initiated after a 
successful attempt during the same breeding 
season, also termed double brooding) are rarely 
observed in raptors, and are thought to be 
uncommon due to the length of the breeding 
cycle (Marti 1969). The frequency of renesting 
and second nesting attempts is likely underesli- 
mated because the female must be individually 
marked and observed at both nests (Fankhauser 
1964). Thus, instances of renests and second nests 
primarily have been those initiated at or near the 
initial nest site (Marti 1969. Millsap and Bear 
1990, Marks and Perkins 1999). Distances moved 
'Environment Canada, Room 200. 4099-98 Avenue 
Edmonton. AB T6H 2X3. Canada. 
2 U.S. Geological Survey, Arizona Cooperative Fish and 
Wildlilc Research Unit, School of Natural Resources and 
the Environment. 325 Biological Sciences East, University 
of Arizona, Tucson. AZ 85721, USA. 
3 Corresponding author, e-mail: 
geoffrey.holroyd @ec.gc.ca 
between first and second nesting attempts within a 
breeding season (i.e., within-year breeding dis¬ 
persal) are frequently not available and are likely 
underestimated for most, if not all. species. 
Migration has been defined as the movement of 
an organism from one location to another either 
permanently (dispersal) or on a seasonal cycle 
(Roff and Fairburn 2001). Migration routes of 
Burrowing Owls (Athene cunicularia) have been 
poorly documented (Haug et al. 1993) due to low 
(1 .5%) band encounter rates (Harman andBarclay 
2007). Burrowing Owls from the Canadian Great 
Plains migrate easl of the Rockies, in a south¬ 
eastern direction, based on 10 band encounters in 
the records of the U.S. Geological Survey’s 
(USGS) Bird Banding Laboratory (BBL) through 
2008, and nine owls with transmitters located in 
wintering areas (Holroyd et al. 2010). Encounters 
ol 16 Burrowing Owls from British Columbia 
banded west of the Rocky Mountains revealed 
they migrated southwest to the U.S. Pacific Coast 
states (Holroyd et al. 2010). 
We document two nesting attempts of a female 
Burrowing Owl within the same breeding season 
in widely separated locations (Arizona aod 
Saskatchewan) that required crossing the Rocky 
Mountains in between the two previously known 
migration routes. 
CHRONOLOGY OF 2003 BURROWING OWL 
NESTING EVENTS 
We located a Burrowing Owl nest site at Davis- 
Monthan Air Force Base (32.2'N, 110.9 Wl on 
14 April 2003 during an intensive demography 
study in Tucson. Arizona. USA (Ogonowski 2007. 
Ogonowski and Conway 2009). A male owl was 
at the burrow entrance and, using an infrared 
video probe, we found a female 2.5 m below 
ground whose body posture was indicative of a 
bird sitting on eggs. On 27 April we observed a 
pair standing at the burrow entrance and. on -’0 
April, we trapped and banded both birds. The 
adult female Burrowing Owl was banded with a 
USGS band and an anodized black aluminum 
rivet band (Acrafl Sign and Nameplate Co., 
Edmonton, AB, Canada) with vertical letters H 
