DOI: 10.5061/dryad.xpnvx0km3
title: Capture histories of owls with covariates for survival analysis

description: Early life experiences have carry-over effects that manifest in later life
 stages. Challenging rearing environments result in more energy invested in
 immediate survival and less energy on growth and maturation, which can
 decrease survival in both the short and long term. One way to measure
 differences in energy allocation to growth between individuals is through
 physiological indices, such as concentrations of the metabolic hormone
 corticosterone, and body condition. Corticosterone increases in response
 to challenges to homeostasis and mobilizes stored fat and muscle to meet
 energetic demands. Maintaining elevated corticosterone can result in poor
 body condition and decreased survival. Juvenile or pre-breeding age
 classes are typically a substantial portion of the total population and
 serve key functions in population dynamics in many long-lived species.
 Thus, understanding how the rearing environment may influence demographics
 across life-history stages is crucial to understanding larger population
 dynamics. Yet, demographic models and conservation planning often lack
 vital rate estimates for early life stages because, prior to breeding,
 animals cannot be effectively sampled (i.e., they are unobservable). We
 used corticosterone concentrations in feathers and body mass of fledged
 juvenile Northern Spotted Owls (Strix occidentalis caurina) as indicators
 of potential energetic limitations early in life and used a multi-state
 modeling framework to quantify the effect of these indicators on apparent
 annual survival prior to claiming a territory (pre-territorial birds) and
 the probability of recruiting into the territorial population. Apparent
 annual survival for pre-territorial birds was higher for birds with
 greater mass, earlier banding dates, and intermediate levels of
 corticosterone. Birds with greater mass at banding were also more likely
 to recruit into the territorial population. Our results demonstrate the
 importance of early development and traditionally excluded life-history
 stages on long-term demographics. Although early life stages are difficult
 to observe, monitoring and conservation efforts may be improved by
 increasing studies on pre-territorial animals, control of Barred Owls, and
 conservation of forest structures important for Spotted Owls. This may
 contribute to increased juvenile survival and recruitment.
description: We used capture histories,
 feathers, and banding data collected from 2001 to 2017 as part of a
 long-term demographic monitoring program for Spotted Owls (e.g., Lint et
 al. 1999). Study areas included Cle Elum and Olympic Peninsula in
 Washington state, and Coast Range, H.J. Andrews, Tyee, Klamath, and South
 Cascades in Oregon state (Figure 1). These study areas cover almost 10% of
 the range of Spotted Owls and have varying topography, climate, land
 management, and forest structure, as described in prior publications
 (e.g., Forsman et al. 2011, Dugger et al. 2016). Cle Elum, Coast Range,
 Tyee, and Klamath study areas contain a blend of federal and private
 lands, while Olympic Peninsula, H.J. Andrews, and South Cascades largely
 cover federal lands. Our field crews monitored historic Spotted Owl
 territories annually, using standard protocols to estimate occupancy,
 survival, and reproductive output of individually marked owls (Franklin et
 al. 1996). After juvenile owls left the nest, surveyors captured and
 banded owls with individually numbered U.S. Fish and Wildlife Service
 bands and color bands. When crews recaptured birds marked as juveniles for
 the first time, they confirmed their USFWS bands and replaced their
 cohort-specific color bands with a unique color-band that allowed
 identification of birds through resighting alone (Forsman et al.,
 1984). During banding, field crews weighed birds and
 collected small samples of body feathers from the breast, back, or head,
 placed them in plastic bags, and stored them at room temperature
 (19–22° C). We collected feathers opportunistically, thus
 the number and feather tract sampled varied. All relevant state and
 federal permits were acquired and maintained for all study areas, and
 protocols for handling owls were approved under animal care and use
 permits overseen by Oregon State University’s Institutional Animal Care
 and Use Committee.