Northern Prairie Wildlife Research Center
James H. Devries, David W. Howerter, Brian L. Joynt, and Robert B. Emery, Institute for Wetland and Waterfowl Research, Ducks Unlimited, Inc., P.O. Box 1160, Stonewall, Manitoba R0C 2Z0 Canada
During 1993-1995, we used 2 attachment techniques to affix transmitters to decoy-trapped and nest-trapped female mallards in the Aspen Parkland biome of prairie Canada. Females decoy-trapped in April were fitted with either a 22-g abdominal implant (DTIM) or a 9-g back-mounted glue-suture design (DTBM). Attachments alternated to avoid temporal bias. Females nest-trapped during May and June were fitted only with the back-mounted design (NTBM). Females were tracked daily following radio attachment until they either hatched a nest or abandoned nesting attempts. When telemetry indicated a female was no longer on the nest, the nest was visited to determine its fate. Hatched nests were indicated by the presence of egg caps and membranes and initial brood size was determined by the number of hatched eggs. A visual count of ducklings was attempted as soon after hatch as possible and periodically thereafter every 7 days until 30 days post-hatch. Number of broods used in the analysis varied by study site as indicated in Table 1. Data for each attachment type were combined over all study sites/years due to small sample sizes in some categories. We used PROC LIFETEST (SAS Institute 1990) to generate 30-day duckling survival probabilities. Multiple comparison tests indicated that duckling survival was lower (P < 0.0001) for broods where the female was decoy-trapped and marked with the back-mounted transmitter. Partial detachment of this back-mounted glue-suture design after several weeks is common, and we speculate that by the time decoy-trapped females hatch a nest, the resulting irritation may lead to reduced vigilance.
Table 1. Number of broods used to examine differences in duckling survival among attachments and attachment date.
|Study Area/Year||Attachment Method (Attachment Date)|
|DTIM (April)||DTBM (April)||NTBM (May-June)|
|Hamiota, MB 1993||12||3||5|
|Erskine, AB 1994||12||5||19|
|Camp Lake, AB 1995||17||8||13|
|Kutawa Lake, SK 1995||12||2||6|
|Shoal Lake, MB 1995||14||2||14|