Abstract
Environmental conditions can exert a strong influence on the growth and energy demands of chicks. We hypothesized that postnatal growth in a cold, aquatic environment would require a high level of energy metabolism in semiprecocial Red-throated Loon (Gavia stellata) chicks. We measured body-mass growth and daily energy expenditure (DEE) of free-ranging chicks in the Arctic. We used daily gains in body mass and DEE to estimate daily metabolizable energy (DME, kJ day(-1)) and total metabolizable energy (TME, kJ chick(-1)). Chicks gained body mass quickly, with a logistic growth rate constant 57% greater than the allometric prediction, yet were at only 60% of adult body mass at fledging. Males grew at a rate similar to that of females but for a slightly longer duration and so reached an asymptotic body mass 23% greater, and tarsus length 8% longer, than that of females. Chick growth performance was similar between first-and second-hatched chicks within broods of 2, which suggests that food availability was not limited. DEE increased in proportion to body mass, and DME peaked at 1,214 kJ day(-1) on day 25 posthatching. Over the average 49-day postnatal period, TME was 49.0 MJ, which is within the range of error of the allometric prediction. Parents provided 58.6 MJ as food to meet this energy requirement. Given this chick energy requirement and the range of energy content of prey observed in the chick diet, selecting prey with higher energy content would greatly reduce adult provisioning effort. Red-throated Loon chicks did not have a high postnatal energy requirement, but rather grew quickly and fledged at a small size-with the effect of reducing the length of the postnatal period and, consequently, parental energy investment in chicks.
| Original language | English |
|---|---|
| Pages (from-to) | 657-670 |
| Number of pages | 14 |
| Journal | Auk |
| Volume | 132 |
| Issue number | 3 |
| Early online date | 3 Jun 2015 |
| DOIs | |
| Publication status | Published - 1 Jul 2015 |
Bibliographical note
We thank C. Hambly, P. Redman, P. Thompson, and L. Vaanholt for the laboratory analysis of the doubly labeled water samples. G. K. Sage and S. Talbot generously conducted the genetic analysis. We are grateful to the Point Lay Village Tribal Council and Cully Corporation for granting access to the study site. L. Ferriera III, J. Neakok, L. Neakok, W. Neakok Sr., L. Neakok, F. Stalker, M. Tracey, and J. Tazruk provided assistance in Point Lay. W. Tracey Sr. provided valuable logistical support. S. Delong, R. Dugan, A. Mangan, K. Overduijn, A. Pagano, A. Pons, K. Pyle, and A.Yoke provided outstanding assistance in the field. P. Barboza provided valuable advice throughout the study. Comments from P. Barboza, A. Gall, M. Lindberg, A. Springer, and two anonymous reviewers improved the manuscript. Any use of trade names is for descriptive purposes only and does not imply endorsement by the U.S. Government.Funding statement: This project was funded by the U.S. Minerals Management Service and the U.S. Geological Survey (USGS) Alaska Science Center's Outer Continental Shelf program. Additional support was provided by the Department of Biology and Wildlife at the University of Alaska Fairbanks. D.J.R. was partially supported by the Betty A. Anderson Memorial Scholarship for Avian Studies.
Keywords
- diver
- energy allocation
- growth rate
- postnatal development