Distinguishing effects of juvenile mortality and dispersal on recruitment |
| |
Authors: | FALINE M. DRUMMOND Kevin A. Parker Tim G. Lovegrove Doug P. Armstrong |
| |
Affiliation: | 1. Wildlife Ecology Group, Massey University, Private Bag, 11222 Palmerston North, New Zealand;2. Parker Conservation, P.O. Box 130, Warkworth, 0941 New Zealand;3. Biodiversity Group, Auckland Council, Private Bag 92300, Victoria Street West, Auckland, 1142 New Zealand |
| |
Abstract: | Detailed data on juvenile survival are rare in the literature. Although many studies estimate recruitment, if you cannot distinguish between permanent dispersal and mortality, the management implications for a population may be unclear. We estimated juvenile survival in a reintroduced North Island robin (Petroica longipes) population in a protected sanctuary surrounded by an unprotected landscape where the species is extirpated. The population has had marginal population growth due to poor recruitment so we modeled 3 types of data (resighting of fledglings, radio-telemetry of independent juveniles, resighting of adults) in an integrated framework to determine the life stages where high mortality was occurring, and to distinguish mortality from dispersal. Approximately 16% of birds that fledged (n = 109) were present at the start of the next breeding season, consistent with recruitment rates from previous years. Low survival in the first 6 weeks after fledging was the primary cause of poor recruitment. Only 50% survived to independence (4 weeks after fledging), and 18% survived to the end of the radio-tracking period (14 weeks), after which juvenile survival matched adult survival. No dispersal from the sanctuary occurred during the radio-tracking period. Juveniles moved between adjacent forest fragments within the sanctuary, but did not leave the sanctuary. This information, which demonstrates the importance of distinguishing between natal mortality and dispersal, is important for ongoing management of the site and selection of future reintroduction sites for this species. © 2019 The Wildlife Society. |
| |
Keywords: | integrated modeling juvenile survival natal dispersal radio-telemetry reintroduction survival analysis translocation |
|
|