The purpose of this project is to obtain baseline information on the current status of resident Canada geese (
Branta canadensis) along Colorado's Front Range urban/suburban corridor. We will attempt to estimate population size each spring, annual population growth rates, annual survival rates, harvest rates, and recruitment rates; track movement patterns of resident geese within and across years; and measure how resident geese respond to various management practices (i.e., hunting seasons and urban control methods). This information is obtained primarily by trapping geese throughout the study area each year and individually marking a large sample of geese with legbands, and a subset of geese with neckbands, and then tracking the status of these marked birds through time. Band recoveries (primarily hunter-killed geese), recaptures of marked geese during annual trapping operations, and resightings of neckbanded geese provide information on the status of marked individuals, and these data can be analyzed to produce estimates of population parameters. This project was initiated in 2003, and fieldwork is expected to continue through 2008. The results presented below are preliminary. Additional analyses will be conducted and presented in future reports.
The overall Front Range urban corridor study area was initially divided into 3 portions: the Northern Front Range (including sites in and near Fort Collins, Greeley, Windsor, Loveland, Longmont, and Boulder); the Denver metropolitan area (including Golden, Wheatridge, Lakewood, Englewood, Denver, and Aurora); and a Southern portion (El Paso and Pueblo counties). These 3 sub-areas were identified because of differences in landscape features, numbers and distribution of resident Canada geese, and hunting pressure; these variables may influence local population dynamics of resident Canada geese.
In 2003, we legbanded 1,886 Canada geese at 21 sites in the Northern Front Range and Denver Metro portions of the study area. We also neckbanded 357 of these legbanded geese. In 2004, we again trapped geese at all of the 2003 sites. We also added several new trapping sites in these areas, as well as sites in Pueblo County in the Southern portion of the study area. As a result of these trapping efforts, in 2004 we legbanded 2,077 geese, and also neckbanded 253 of these geese. In addition, a total of 724 geese banded in 2003 were recaptured during trapping operations in 2004 (38% of total 2003 bandings). Of these recaptures, 58 were legbanded as goslings (22% of all goslings banded in 2003), 510 were legbanded as adults (40% of adults legbanded only in 2003), and the remaining 156 were legbanded and neckbanded as adults (43% of adults legbanded and neckbanded in 2003).
In 2005, we legbanded 1,669 Canada geese at sites in all 3 portions of the study area; new banding sites were added in Colorado Springs, and 2 new sites were added in the Northern Front Range portion of the study area. We neckbanded 286 of the adult geese banded in 2005. We also recaptured 1,226 geese that had been banded in the study area in 2003 (556) and 2004 (670). These recaptures represent 29% and 32% of the total number of geese banded in 2003 and 2004, respectively.
Legband and neckband loss are important issues, because marker loss can have significant impacts on the estimation of parameters of interest (survival rates, harvest rates, etc.) unless rates of marker loss are estimated and accounted for. In 2004, we recaptured 156 geese that were double-marked with legbands and neckbanded in 2003. Four (2.6%) of these geese had lost their neckbands, and an additional 15 (9.6%) had cracked or broken neckbands which were replaced. Seven (4.5%) recaptured geese had lost their legbands but retained their neckbands. In 2005, we recaptured 172 geese that were double-marked in previous years. Thirteen (7.6%) of these geese had lost their neckbands, and 35 (20.3%) had cracked or broken neckbands which were replaced. Four (2.3%) recaptured geese had lost their legbands but retained their neckbands.
As of June 2005, a total of 63 geese marked in 2003 (3.3% of the total marked sample) had been reported shot during the 2003-04 hunting seasons. An additional 94 (5.0%) geese marked in 2003 were reported shot during the 2004-05 hunting seasons. A total of 161 (7.8%) of geese marked during 2004 were reported shot during the 2004-05 hunting seasons. Over the past 2 hunting seasons, a larger proportion of geese marked in the Northern Front Range portion of the study area (14.2%) have been harvested than geese marked in the Denver Metro portion of the study area (3.3%).
An additional 18 banded geese have been reported as dead due to causes other than hunting, including being struck by a motor vehicle (8), killed by a dog or other animal (3), and unspecified injuries (7). These recoveries, along with the 318 hunter-shot geese reported to date, total 336 (8.5%) of the total sample of geese banded during 2003 and 2004.
In 2006, we plan to trap and mark geese at all locations used in 2004. Because recaptures are becoming common, we may need to add a few additional banding sites in each portion of the study area in order to maintain adequate samples of newly-marked geese. Numerous CDOW staff and volunteers have provided valuable assistance with annual trapping and marking of geese, and their contributions are critical to the success of this project.