Condition Bias of Decoy‐Harvested Light Geese During the Conservation Order

Abstract

Evidence that decoy harvest techniques primarily remove individuals of poorer body condition is well established in short‐lived duck species; however, there is limited support for condition bias in longer‐lived waterfowl species, such as geese, where decoy harvest is considered primarily additive because of their high natural survival rates. We evaluated support for the harvest condition bias hypothesis of 2 long‐lived waterfowl species, the lesser snow goose (Anser caerulescens caerulescens) and Ross's goose (Anser rossii). We used proximate analysis to quantify lipid and protein content of lesser snow and Ross's geese collected during the Light Goose Conservation Order (LGCO) in 2015 and 2016 during spring migration in Arkansas, Missouri, Nebraska, and South Dakota, USA. In each state, LGCO participants collected birds using traditional decoy techniques and we collected birds from the general population using jump‐shooting tactics. Total body lipid content in both lesser snow and Ross's geese varied with age, region of harvest, and harvest type (decoy or jump‐shooting). On average, adult lesser snow and Ross's geese harvested over decoys had 60 g and 41 g, respectively, fewer lipids than conspecifics collected using jump‐shooting. We observed lower lipid reserves in decoy‐shot geese in all 4 states sampled despite general gains in lipid reserves as migration chronology progressed. Our data support that the harvest condition bias extends to longer‐lived waterfowl species and during a life‐history event (spring migration) in which harvest is not normally observed. In the case of overabundant light geese, the disproportionate harvest of poorer‐conditioned lesser snow and Ross's geese may serve as an additional challenge against any realized effects of harvest to reduce the population, in addition to extremely low harvest rates. © 2019 The Wildlife Society.

Evidence for synergistic cumulative impacts of marking and hunting in a wildlife species

“…Results from LeTourneux et al (2021) support this by providing evidence that geese use food‐rich agricultural fields less when they are in good body condition, probably because these habitats represent a high risk due to hunting activity. This is also in line with recent work by Fowler et al (2019) showing that lesser snow geese ( Anser caerulescens c .) shot over decoys during spring migration are in poorer condition than those from the general population.…”

“…Nonetheless, a reduced condition of collared birds could also contribute to an increase in crippling loss if birds in poor condition take greater risks and get closer to hunters (e.g. Fowler et al, 2019). This effect might be exacerbated further if hunters target collared geese that are too far to be killed effectively.…”

“…Therefore, nonhunting mortality of neck‐collared birds could increase if chronic stress reduces their body condition and increases predation or exhaustion risks. Alternately, hunting mortality could increase if geese in lower condition become more vulnerable to hunting (Fowler et al, 2019, but see Morez et al, 2000).…”

Effects of mass capture on survival of greater white‐fronted geese in Alaska

“…In support of our reasoning, our data did not support evidence of an association between holding time and recovery probabilities, which may have indicated that lower survival of the longest held individuals was related to increased harvest mortality or that we may have unknowingly selected higher or lower quality individuals in the order that we processed geese. For example, Fowler et al (2020) reported that lesser snow geese and Ross's geese ( A. rossii ) in poorer condition were disproportionately harvested by hunters at higher rates.…”

Nasal Discs and the Vital Rates of Lesser Scaup

“…Furthermore, our findings about brood-rearing body condition at the onset of autumn are consistent with a lack of evidence for recovery probability and recovery distance varying with nasal-disc state. This is because below-average body condition is linked to higher recovery probability for ducks and geese (Greenwood et al 1986, Dufour et al 1993, Fowler et al 2020). Thus, our findings for recovery probability contrast with results for Ross' geese that indicate neck collars may decrease body condition or change behavior such that survival decreases and recovery increases (Caswell et al 2012).…”