Estimating recruitment rate and population dynamics at a migratory stopover site using an integrated population model

Abstract

Consideration of the full annual cycle population dynamics can provide useful insight for conservation efforts, but collecting data needed to estimate demographic parameters is often logistically difficult. For species that breed in remote areas, monitoring is often conducted during migratory stopover or at nonbreeding sites, and the recruitment rate of new breeding adults can be difficult to estimate directly. Here, we present an integrated population model that uses mark-resight and count data to estimate survival probability, population growth rate, and recruitment rate for an Arctic-breeding shorebird of conservation concern, the red knot (Calidris canutus rufa), from data collected during spring stopover in Delaware Bay, USA, from 2005 to 2018. At this site, red knots feed primarily on the eggs of spawning horseshoe crabs (Limulus polyphemus), a legally harvested species. We used this model to estimate the relationship between horseshoe crab abundance and red knot demographics, which informed a recent revision to the framework used to establish horseshoe crab harvest regulations. Our analysis indicates that the red knot population was most likely stable from 2005 to 2018 (average λ = 1.03, 95% credible

Survival of red knots in the northern Gulf of Mexico

“…islandica) wintering in Great Britain was maintained by alternating trends of survival and recruitment, implicating a potential role of density-dependent processes in population regulation. Knots using Delaware Bay during spring migration experienced consistently high apparent survival which was offset by consistently low recruitment between 2005-2018, resulting in a slightly positive population growth rate (Tucker et al, 2023). Using data from two large shorebird monitoring datasets, Bart et al (2007) suggested the most likely mechanisms of North American shorebird population declines are reduction in breeding population size and poor reproduction, rather than an artifact potentially explicable by shifting distributions.…”

Assessment of recovery potential for the American horseshoe crab (Limulus polyphemus): An application of the IUCN green status process

“…However, modelling methods have advanced to help make the best inference possible from available data through analysis of multiple information sources (Schaub & Kéry, 2022; Anstead et al, 2023). Such methods have been used to combine multiple surveys to estimate horseshoe crab abundance and to combine mark–recapture and aerial counts to estimate the abundance and survival of the horseshoe crab‐reliant red knots in Delaware Bay (Atlantic States Marine Fisheries Commission (ASMFC), 2022a; Tucker et al, 2023). Greater use of these methods could be explored throughout the horseshoe crabs’ range to better prepare for future assessments.…”