Intercolony variation in growth of black brant goslings on the Yukon‐Kuskokwim Delta, Alaska

Abstract

Recent declines in black brant (Branta bernicla nigricans) are likely the result of low recruitment. In geese, recruitment is strongly affected by habitat conditions experienced by broods because gosling growth rates are indicative of forage conditions during brood rearing and strongly influence future survival and productivity. In 2006–2008, we studied gosling growth at 3 of the 4 major colonies on the Yukon‐Kuskokwim Delta, Alaska. Estimates of age‐adjusted gosling mass at the 2 southern colonies (approx. 30% of the world population of breeding black brant) was low (gosling mass at 30.5 days ranged 346.7 ± 42.5 g to 627.1 ± 15.9 g) in comparison to a third colony (gosling mass at 30.5 days ranged 640.0 ± 8.3 g to 821.6 ± 13.6 g) and to most previous estimates of age‐adjusted mass of brant goslings. Thus, our results are consistent with the hypothesis that poor gosling growth is negatively influencing the brant population. There are 2 non‐mutually exclusive explanations for the apparent growth rates we observed. First, the population decline may have been caused by density‐independent factors and habitat capacity has declined along with the population as a consequence of the unique foraging feedback between brant and their grazing habitats. Alternatively, a reduction in habitat capacity, as a result of changes to the grazing system, may have negatively influenced gosling growth, which is contributing to the overall long‐term population decline. We found support for both explanations. For colonies over habitat capacity we recommend management to enhance foraging habitat, whereas for colonies below habitat capacity we recommend management to increase nesting productivity. © 2010 The Wildlife Society.

Trade‐offs between offspring fitness and future reproduction of adult female black brent

“…Substantial spatial variation exists in gosling growth rates at TR similar to other studies of geese (Cooch et al. 1991; Larsson & Forslund 1992; Fondell et al. 2011).…”

Density dependence and phenological mismatch: consequences for growth and survival of sub-arctic nesting Canada Geese

“…Indeed, the per capita availability of high quality forage affects gosling growth rates (Lindholm et al 1994, Sedinger et al 2001, Lake et al 2008, Fondell et al 2011), which in turn could negatively affect components of population dynamics (Schmutz 1993, Shorrocks et al 1998, Cooch et al 2001, Nicolai et al 2014. Density of conspecifics and ecologically similar species can also limit forage availability through exploitation and interference competition (Loonen et al 1997, Sedinger et al 1998, Schmutz and Laing 2002.…”

“…For example, foraging by geese can increase plant productivity through a feedback mechanism in which moderately grazed vegetation can produce higher quality forage for longer compared to plants that are not grazed (Harwood 1977, Bazely and Jefferies 1986, 1989, Hik and Jefferies 1990, Person et al 2003. Similarly, grazing may change the phenotype of some species from a low quality to a high quality forage, thus increasing available feeding habitat (Person et al 2003, Fondell et al 2011. However, overgrazing is detrimental (Kuijper et al 2009) and can result in generally lower gosling growth rates (Cooch et al 1991a, b, Williams et al 1993, Sedinger et al 2001.…”

Full Issue

“…Growth rates of hatchlings can be indicators of forage quality and availability and general habitat suitability of brood-rearing areas (Lepage et al 1998, Audet et al 2007, Fondell et al 2011. Growth rates can also be directly related to fledging success by influencing the duration of the flightless period, when young are most vulnerable to predation (Mauser et al 1994, Pearse andRatti 2004).…”