Effects of El Niño on Distribution and Reproductive Performance of Black Brant

Abstract

Climate in low-latitude wintering areas may influence temperate and high-latitude breeding populations of birds, but demonstrations of such relationships have been rare because of difficulties in linking wintering with breeding populations. We used long-term aerial surveys in Mexican wintering areas and breeding areas in Alaska, USA, to assess numbers of Black Brant (Branta bernicla nigricans; hereafter brant) on their principal wintering and breeding area in El Niño and non-El Niño years. We used Pollock's robust design to directly estimate probability of breeding and apparent annual survival of individually marked brant at the Tutakoke River (TR) colony, Alaska, in each year between 1988 and 2001. Fewer brant wintered in Mexico during every El Niño event since 1965. Fewer brant were observed on the principal breeding area following each El Niño since surveys began in 1985. Probability of breeding was negatively related to January sea surface temperature along the subtropical coast of North America during the preceding winter. Between 23% (five-year-olds or older) and 30% (three-year-olds) fewer brant nested in 1998 following the strong El Niño event in the winter of 1997-1998 than in non-El Niño years. This finding is consistent with life history theory, which predicts that longer-lived species preserve adult survival at the expense of reproduction. Oceanographic conditions off Baja California, apparently by their effect on Zostera marina (eelgrass), strongly influence winter distribution of brant geese and their reproduction (but not survival), which in turn affects ecosystem dynamics in Alaska.

Ecosystem‐scale loss of grazing habitat impacted by abundance of dominant herbivores

“…Our grazing lawn abundance estimates correspond to previous estimates that also found higher abundance during the 1990s (Person et al 2003, Sedinger et al 2016. Changes in the number of nesting brant have also been linked to variation in abundance and availability of their primary food source (eelgrass), during the nonbreeding period (Ward et al 2005, Sedinger et al 2006) and local subsistence harvest (Sedinger et al 1993). This increase was interpreted as recovery from a period of high fox predation and low nest success in the 1980s (Person et al 2003).…”

Characteristics of climate and landscape disturbance influence the dynamics of greater sage‐grouse populations

“…For each, we estimatedĉ based on v 2 /df from the goodness-of-fit test in RDSURVIVE, and corrected for overdispersion by adjusting AIC c values to QAIC c ifĉ was greater than 1.0 (Burnham and Anderson 2002). Meaningful sources of potential heterogeneity, such as age-or lek-specific covariate effects, cannot be easily incorporated in RDSURVIVE, so our goodness-of-fit testing likely provides an overly conservative approximation ofĉ (Sedinger et al 2006).…”

Factors influencing route choice by avian migrants: A dynamic programming model of Pacific brant migration

“…In reality foraging decisions will also be affected by tidal events (Moore and Black, 2006) but the inclusion of such a time variable would make the model very complex. For obvious reasons we also neglect El Nin˜o events even though these will have considerable effect on migration in the black brant (Sedinger et al, 2006).…”