Apparent survival, natal philopatry, and recruitment of Barrow’s goldeneyes (Bucephala islandica) in the Cariboo–Chilcotin region of British Columbia, Canada

Abstract

We used capture–resight data to evaluate apparent survival, natal philopatry, and recruitment of Barrow’s goldeneyes ( Bucephala islandica (Gmelin, 1789)) in British Columbia, Canada. Median ages of first pairing and first breeding for females were 2 years and 3 years, respectively. The Cormack–Jolly–Seber model that best fit our data indicated that apparent survival rates (Φ) differed according to sex, year, and age class at marking. Estimates were similar for after-hatch-year (AHY) females (0.62) and AHY males (0.58), which was consistent with predictions. However, contrary to predictions, apparent survival rates of hatch-year (HY) females (0.68) were similar to those of AHY females and significantly higher than those of HY males (0.35). We interpret this difference as being primarily related to higher dispersal probabilities by HY males. Also evident was a negative correlation between apparent survival rate during the 1st year after capture for HY birds and their subsequent apparent survival rates, which suggests that probability of dispersal increased after these birds reached reproductive maturity and began to compete for breeding territories. We interpret this as evidence for density-dependent control of access to limited resources such as nest cavities.

Life history patterns, individual heterogeneity, and density dependence in breeding common goldeneyes of the northern boreal forest

“…Therefore, to the extent that we underestimated φ A we must have overestimated φ J . Our average post‐fledging survival estimate (φ J’ ; x = .16 ± 0.05) is significantly lower than existing estimates for female Barrow's goldeneyes (0.68; Boyd et al ). However, we were unable to further adjust for potential sex differences in survival because detection probability for males was zero in our study.…”

“…The lower post‐fledging survival estimates we report may reflect potential differences in mortality or dispersal patterns compared to Boyd et al's (2009) study. Our study population is near the northern distributional limit of the goldeneye's breeding range (Eadie et al ), and may be subject to harsher wintering conditions, longer migration, and a more constrained nesting phenology, all of which may create different mortality patterns, relative to temperate latitude populations (Boyd et al ). Alternatively, nest sites may have been more limited in our study population compared to Boyd et al's (2009), leading to higher natal dispersal that lowered our estimates of post‐fledging survival.…”

“…We recognize that our first‐year survival estimate was biased low due to the inclusion of both sexes, as only females were available for recruitment. Other studies in sea ducks estimated first‐year survival based on returns of individuals marked near, or post‐fledging (Boyd et al , Oppel and Powell ). Therefore, to compare our estimates to existing studies, we assumed a primary sex ratio of 1:1 in our marked sample (Swennen et al , Blums and Mendis ), and multiplied our φ J estimates by two to account for our inability to detect males.…”

Identifying demographic and environmental drivers of recruitment and population growth in a cavity‐nesting sea duck population

“…The negative density‐dependent relationship between conspecific nest box occupancy during prospecting and subsequent recruitment could be explained through multiple demographic processes, including reduced second‐year survival, delaying recruitment, increased likelihood of engaging in alternative nesting strategies at recruitment, or natal dispersal. Adult survival, which is assumed to be similar to second‐year survival rates in sea ducks (Boyd et al , Schamber et al ), in our study population is relatively high (0.86 ± 0.11, Lawson et al ) and did not appear to be controlled by density‐dependent factors. The individual probability of recruitment for individuals that survived to two years of age is also very high (0.96 ± 0.06, Lawson et al ), and suggests that goldeneyes in our study population begin breeding as early as possible, rather than delaying recruitment.…”

“…Though natal philopatry and breeding site fidelity are assumed to be high in goldeneyes (Savard and Eadie , Pöysä et al ), a recent study of the closely related Barrow's goldeneye in British Columbia, Canada reported that only a small proportion of yearling females that returned to their natal grounds for nest prospecting were actually recruited into the breeding population (Boyd et al ). The authors detected a negative correlation between first‐year apparent survival and subsequent within‐cohort apparent survival, and suggested that within‐cohort density dependence may reduce local recruitment (Boyd et al ), though nest site availability was not examined. However, we evaluated the effect of first‐year survival on subsequent recruitment rates and population growth for cohorts but found no support for an effect of first‐year survival (models containing dphi t‐ 1 in Supplementary material Appendix A Table A1, A2).…”