Pamela R. Garrettson

Effects of mammalian predator removal on production of upland-nesting ducks in North Dakota

In the Prairie Pothole Region, high predation rates often reduce duck nest success below the 15-20% deemed necessary for population stability. Lethal removal of mammalian predators is 1 potential management option, but little reliable information exists on the efficacy of this technique. We trapped 8 41.5 km 2 blocks during April-July 1994-1996, and found higher nest success on trapped sites (x = 42%; 37-46%, 95% CI) than on untrapped sites (x = 23%; 19-25%, 95% CI). We found that daily survival rates increase with nest age and later nest initiation date, and we adjusted for this heterogeneity when we calculated nest success. There were no year or year x treatment effects on nest success. From 1 year to the next, pair numbers tended to increase more on trapped sites than on untrapped sites for all dabbling ducks combined. Removal of mammalian predators dramatically increases duck nest success, but its use as a management tool will also depend on its acceptance by the public.

THE EFFECT OF REWARD BAND VALUE ON MID‐CONTINENT MALLARD BAND REPORTING RATES

Knowledge of annual waterfowl harvest rates is important to North American waterfowl population management. In particular, harvest rate is a critical parameter governing the relationship between population status and regulatory packages within the adaptive harvest management (AHM) framework by which the U.S. Fish and Wildlife Service (FWS) manages mallard populations (Williams and Johnson 1995, Johnson et al. 1997, Johnson 1999). Annually, in conjunction with many state and provincial agencies and the Canadian Wildlife Service (CWS), the FWS places bands on waterfowl to obtain information about their vital rates, especially survival and harvest. If all harvested banded birds were reported, harvest rates could be estimated directly by the proportion of banded birds that were recovered (the recovery rate). However, an adjustment to this calculation must be made because not all banded waterfowl that are har-

Effects of backpack and implanted radiotransmitters on captive blue-winged teal

Radiotelemetry is frequently used for research on waterfowl, but some transmitter designs alter reproductive effort, behavior, and mass of birds. Quantitative comparisons of transmitter effects are needed so rescarchers can use instruments least likely to generate biased results. We compared body mass and behavior of captive blue-winged teal (Auds discors) females fitted with either a backpack-harness transmitter, abdominally implanted device or no racho over a 12-week period. Females with implants lost mass during the first week following surgery, while backpack-marked and control birds gained mass (P = 0.02). Mass of implanted birds recovered by the second week after surgery, and never differed among treatment groups over the subsequent 11 weeks (P ≥ 0.51) Females with backpack transmitters spent more time on comfort movements (P 0.18), feeding (P ≥ 0.10). or on locomotion (P ≥ 0.18). except that backpack-marked females spent less time engaged in locomotion than did implanted females (P = 0.03). Out results corroborate previous studics showing effects of backpack-harness transmitters on behavior. We demonstrated that implants do not affect behavior, but are associated with a temporary post-surgical loss of mass The alteration of behavior eaused by backpack tranmitters did not diminish with time, so researchers should not assume that an adjustment period is sufficient to climinate transmitter effects.

Predicting Wood Duck Harvest Rates in Eastern North America

Abstract We developed a method for predicting wood duck (Aix sponsa) harvest rates in eastern North America using waterfowl banding and recovery data, annual indices of hunter numbers, and harvest survey data from the United States and Canada. We predicted that under the current season length (60 days), if hunter numbers remain unchanged, increasing the wood duck bag limit from 2 to 3 would increase harvest of adult male wood ducks in the Atlantic and Mississippi flyways by 12.3%, causing an increase in harvest rate of 7.1% from 0.087 to 0.093. The Flyway Councils and the United States Fish and Wildlife Service can consider this information to predict the impacts of regulatory changes.

Integrating Breeding Bird Survey and demographic data to estimate Wood Duck population size in the Atlantic Flyway

ABSTRACT The U.S. Fish and Wildlife Service (USFWS) uses data from the North American Breeding Bird Survey (BBS) to assist in monitoring and management of some migratory birds. However, BBS analyses provide indices of population change rather than estimates of population size, precluding their use in developing abundance-based objectives and limiting applicability to harvest management. Wood Ducks (Aix sponsa) are important harvested birds in the Atlantic Flyway (AF) that are difficult to detect during aerial surveys because they prefer forested habitat. We integrated Wood Duck count data from a ground-plot survey in the northeastern U.S. with AF-wide BBS, banding, parts collection, and harvest data to derive estimates of population size for the AF. Overlapping results between the smaller-scale intensive ground-plot survey and the BBS in the northeastern U.S. provided a means for scaling BBS indices to the breeding population size estimates. We applied these scaling factors to BBS results for portions of the AF lacking intensive surveys. Banding data provided estimates of annual survival and harvest rates; the latter, when combined with parts-collection data, provided estimates of recruitment. We used the harvest data to estimate fall population size. Our estimates of breeding population size and variability from the integrated population model (N̄ = 0.99 million, SD = 0.04) were similar to estimates of breeding population size based solely on data from the AF ground-plot surveys and the BBS (N̄ = 1.01 million, SD = 0.04) from 1998 to 2015. Integrating BBS data with other data provided reliable population size estimates for Wood Ducks at a scale useful for harvest and habitat management in the AF, and allowed us to derive estimates of important demographic parameters (e.g., seasonal survival rates, sex ratio) that were not directly informed by data.

An Evaluation of June Wood Duck Banding in the Southern Atlantic Flyway

Abstract In waterfowl banding studies, the preseason banding period is commonly accepted as July through September; however, in an effort to increase Aix sponsa (Wood Duck) banding in the Atlantic Flyway, several state agency biologists have considered banding Wood Ducks in June. We analyzed existing Wood Duck banding data to determine if direct band-recovery rates of Wood Ducks banded in June differed from those banded during July—September. We calculated direct recovery rates by state, month, and year for 1998–2007 at selected states in the Atlantic Flyway. Arcsine-transformed direct band-recovery rates differed by month of banding (P = 0.0099; F = 3.973; df = 3, 111) and were lower in June than in July or August. We suggest that state or federal agencies conducting Wood Duck banding should spend their time and effort during the traditional banding period 1 July—30 September.