Climatic Effects on Grey-Faced Petrel (Pterodroma gouldi) Chick Growth and Survival

Abstract

Grey-faced Petrels (Pterodroma gouldi) are a colonial burrowing seabird predominantly nesting on offshore islands of the upper North Island of New Zealand. We studied their annual breeding biology and the impact of Southern Oscillation Index climatic effects by measuring colony productivity and chick growth rates from 2011 to 2015 on Te Hāwere-a-Maki as unfavorable warmer La Niña conditions changed to favorable cooler El Niño conditions. Across all five years, annual chick hatching consistently occurred within a one-week period at the end of August but fledging variably occurred over a three-week period following Christmas. Because ship rats are pest controlled on Te Hāwere-a-Maki, we found only a slight reduction in breeding success with nearby predator-free islands. However, chick growth and fledging rates were significantly higher under El Niño conditions occurring towards the end of our study, rather than La Niña conditions at the start of our study. Our regular handling of chicks for monitoring had no discernible impact compared to a set of control chicks. The combined impacts of annual variation in predation and climate mean the Grey-faced Petrel colony on Te Hāwere-a-Maki maintains a constant population size of around 100 burrows.

Chick Provisioning in Grey-Faced Petrel (Pterodroma gouldi) under Environmental Stress

“…We found no significant difference in rates of body mass loss between years, noting that both years were periods of known environmental stress for Grey-faced Petrel chick rearing due to La Niña conditions [18]. Although we do not have comparative chick provisioning data during El Niño conditions, chicks are known to grow and survive better in such years [18], presumably due to better provisioning in some way (i.e., any of provisioning rate, meal size or meal quality).…”

“…We found no significant difference in rates of body mass loss between years, noting that both years were periods of known environmental stress for Grey-faced Petrel chick rearing due to La Niña conditions [18]. Although we do not have comparative chick provisioning data during El Niño conditions, chicks are known to grow and survive better in such years [18], presumably due to better provisioning in some way (i.e., any of provisioning rate, meal size or meal quality). Although the rate of body mass loss did not differ between chicks that subsequently went on to successfully fledge or not, the body mass of chicks entering our study differed significantly between chicks that subsequently went on to successfully fledge or not.…”

“…Our short study period of 10 days in both years was unable to determine long-term trends in chick provisioning across the entire chickrearing period where accumulated differences in chick provisioning by adults would lead to substantial body mass gain differences among chicks. However, fortnightly measurements of chick growth across the entire chick-rearing period in the same years have shown such substantial differences [18].…”

“…and rats (Rattus spp.). However, La Niña events of the El Niño Southern Oscillation reduce chick growth rates and fledgling success on these islands [18]. La Niña conditions bring more north-easterly winds, and warmer seas occur towards northern New Zealand [19].…”

Consistent seasonal foraging niche segregation between critically endangered Whenua Hou Diving Petrels and abundant Common Diving Petrels

“…El Niño conditions are characterized by cooler waters, whereas La Niña conditions are characterized by warmer waters (Mullan 1995, Russell et al . 2022). Common Diving Petrels appeared to be sensitive to ENSO cycles, as both incubation and non‐breeding foraging niches shrank during El Niño conditions.…”