Evidence for high inter-generational individual quality in yellow-eyed penguins

Abstract

Longitudinal studies focusing on lifetime reproductive success (LRS) have been used to measure individual breeding performance and identify commonalities among successful breeders. By extending the focus to subsequent generations we identify a proportion of high-quality individuals that contribute disproportionately to the population over multiple generations. We used 23 years of yellow-eyed penguin (Megadyptes antipodes) breeding data from one breeding area to identify the proportion of individual birds that raised successful breeders, which in turn raised offspring. We explored which life-history components influenced LRS, as this knowledge would enable conservation resources to be focused on high-performing individuals in this endangered population. From 2,147 birds marked as chicks, 370 (17.2%) survived to adulthood and recruited to their natal location, of which 219 (10.2%) fledged offspring: 124 (56.6%) of the 219 birds produced offspring that recruited as breeders. Only 102 birds (4.8% of 2,147) fledged first-generation offspring that in turn fledged offspring (second-generation offspring, or grand-offspring). We found that ∼25% of the birds that survived to breed had above-average LRS as well as above-average numbers of grand-offspring, and were more likely to have produced first-generation chicks that recruited and also produced above-average numbers of second-generation chicks. Our findings suggest that there is a core of “super-breeders” that contribute disproportionately to the population over successive generations. Lifespan and age-at-first-breeding were correlated with LRS. We suggest that traits of birds relating to longevity, health (e.g., immunocompetence) and fitness could be examined to identify potential links with high LRS and inter-generational fecundity. “Super-breeders” appear to consistently achieve high LRS and long lifespans in a stochastic environment, demonstrating greater resilience in the face of extreme events.

Fat chance? Endangered penguin rehabilitation has mixed conservation outcomes

“…Evaluating chick body mass as they approach their asymptotic size at c. 70d (van Heezik, 1990) would allow early intervention before body condition has deteriorated to the point of emaciation (van Heezik, 1990), as was observed with most chicks that were removed for rehabilitation. Post-fledging survival probability was 23.1% for all marked chicks that fledged, regardless of intervention, from 2007/08 to 2014/15, which is comparable to previously reported post-fledging recovery rates from resightings (20.5%, Stein et al, 2017;20.8%, Efford, Darby, & Spencer, 1996). Heavier, wild-fledging yellow-eyed penguin chicks had the highest probability of survival (0.38), whereas rehabilitated chicks had a significantly lower post-fledging survival probability, despite being consistently heavier at fledging than wild-fledged chicks.…”

“…Age-at-first-breeding is highly variable for yellow-eyed penguins (2-12 years, Stein et al, 2017), but c. 90% of known-age birds that survive the immature period (postfledging to pre-recruitment) commence breeding by age five (M.J. Young and A.M. Stein, University of Otago, unpublished data). We therefore considered the apparent survival rates of wild-fledged and rehabilitated chicks for each cohort from fledging up to the age of five.…”

“…We determined the apparent survival and breeding propensity of adults from re-sighting, nesting, and mortality data, from the YEPDB up to 3 years following a breeding event (i.e., for birds that bred in the 2013/14 season, we considered breeding, re-sighting or mortality information up to the end of the 2016/17 season). If an adult bird bred in year n, but was not re-sighted in year n + 1, n + 2 or n + 3, it was assumed to have died (after Stein et al, 2017). If a bird bred in year n, was not re-sighted in year n + 1, but was re-sighted in year n + 2 and/or year n + 3, it was classed as alive and not breeding in year n + 1.…”

“…The objectives of this study were to: (a) demonstrate the value of using a rehabilitation database in conjunction with a long-term monitoring database; (b) assess success in terms of survival of rehabilitated underweight yellow-eyed penguin chicks taken from the wild for supplementary feeding, in relation to their admission mass, and describe reasons for admission and time spent in temporary captivity; (c) compare the probability of survival post-fledging of rehabilitated chicks to that of wildfledged chicks; and (d) determine if the removal of underweight chicks was associated with improved survival or breeding propensity of adults in the following breeding season. Measuring the longer-term success of rehabilitation of underweight chicks has been difficult due to low juvenile survival (20.5%; Stein, Young, Darby, Seddon, & van Heezik, 2017) and low re-sighting probability of immatures until they recruit into the breeding populations (Maness & Anderson, 2013). By using data collected over 13 years and stored in a long-term monitoring database we were able to evaluate the survival of wild-fledging and rehabilitated individuals, and their respective parents, post-intervention.…”

Consistent Site-Specific Foraging Behaviours of Yellow-eyed Penguins/Hoiho Breeding on Stewart Island, New Zealand

“…Yellow-eyed penguins have undergone rapid decline since the 1990s despite terrestrial intervention undertaken by local conservation managers and community groups [ 6 , 31 , 32 ]. The species is long-lived, c. 24 years [ 33 ] and can maximise reproductive effort through equal rearing of both chicks when experiencing favourable foraging conditions; however, survival of chicks and adults has been compromised by starvation [ 34 , 35 ], entanglement in gillnets [ 17 , 36 ], predation by introduced mammals [ 34 , 37 ], and disease [ 38 ]. Richdale [ 39 ] identified juvenile survival to adulthood to be naturally low, and this has since further declined to c. 12% [ 33 ].…”