Seasonal home range dynamics and sex differences in habitat use in a threatened, coastal marsh bird.

Jaan R Kolts,Susan B Mcrae

doi:10.1002/ece3.2761

Abstract

A comprehensive understanding of spatiotemporal ecology is needed to develop conservation strategies for declining species. The king rail (Rallus elegans) is a secretive marsh bird whose range historically extended across the eastern United States. Inland migratory populations have been greatly reduced with most remaining populations inhabiting the coastal margins. Our objectives were to determine the migratory status of breeding king rails on the mid‐Atlantic coast and to characterize home range size, seasonal patterns of movement, and habitat use. Using radiotelemetry, we tracked individual king rails among seasons, and established that at least a segment of this breeding population is resident. Mean (±SE) home range size was 19.8 ± 5.0 ha (95% kernel density) or 2.5 ± 0.9 (50% kernel density). We detected seasonal variation and sex differences in home range size and habitat use. In the nonbreeding season, resident male home ranges coincided essentially with their breeding territories. Overwintering males were more likely than females to be found in natural emergent marsh with a greater area of open water. Females tended to have larger home ranges than males during the nonbreeding season. We report for the first time the use of wooded natural marsh by overwintering females. Brood‐rearing king rails led their young considerable distances away from their nests (average maximum distance: ~600 ± 200 m) and used both wooded natural and impounded marsh. King rails moved between natural marsh and managed impoundments during all life stages, but the proximity of these habitat types particularly benefitted brood‐rearing parents seeking foraging areas with shallower water in proximity to cover. Our results demonstrate the importance of interspersion of habitat types to support resident breeders. Summer draining of impounded wetlands that are seasonally flooded for wintering waterfowl allows regrowth of vegetation and provides additional habitat at a critical time for wading birds.

Highlights

Animal migration is an adaptive response to changes in ephemeral resources, intraspecific competition, and predator avoidance (Alerstam & Hedenstrom, 1998; Cox, 1968; Greenberg, 1980)
Establishing migratory status is important for sustaining species at risk
Individual variation in habitat use can lead to population structuring (Parrish & Sherry, 1994)

Summary

Introduction

Animal migration is an adaptive response to changes in ephemeral resources, intraspecific competition, and predator avoidance (Alerstam & Hedenstrom, 1998; Cox, 1968; Greenberg, 1980). If a declining species is migratory, preserving wintering or stopover habitat becomes of great importance. An animal’s home range can be influenced by density-dependent variables such as population size (Wunderle, 1995), intraspecific competition (Greenberg, 1986), habitat quality (Kelley et al, 2011), and resource availability (Rolando, 1998). Habitat characteristics that affect home range size in turn impact local distribution and abundance (Morris, 1987). Identifying critical habitat requirements for rare and declining species can inform the implementation and timing of management interventions. For instance, the intentional periodic flooding of impounded aquatic areas can enhance accessibility of vegetation and invertebrate species that benefit many avian wetland obligates (Conway, Eddleman, Anderson, & Hanebury, 1993)

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Discussion

Conclusion