Survival of wild and farmed-released mallards: the Swedish example

Abstract

More than three million farmed mallards are released annually for hunting purposes in Europe. The ecological impact of these releases depends on how many birds survive to join the wild breeding population. We estimated annual survival in farmed-released and wild-caught Swedish mallards, using mark-recapture data. In 2011–2018, we ringed 13,533 farmed ducklings before release (26.5% recovered). Most recoveries were birds shot at the release site, while only about 4% were found >3 km away. In 2002–2018, 19,820 wild mallards were ringed in Sweden, yielding 1369 (6.9%) recoveries. Like in farmed-released birds, most recoveries were by hunting, but 91.1% of recovered wild mallards were >3 km away from the ringing site. Annual survival rate in farmed-released mallards (ringed as pulli) was 0.02. In wild mallards (ringed as fledged or fully grown), annual survival was lower in females (0.64) than in males (0.71). At two sites in 2018, farmed ducklings were released in two batches 3 weeks apart to study the effect of early versus late release date, while controlling for body condition (BCI). Ducklings released early had a higher BCI and were recovered earlier (lower longevity) than those released late. Individual BCI and longevity were not correlated in recovered ducklings. Based on our estimate of annual survival in farmed-released mallards, a substantial number, i.e., 5000 (95% CI, 3040–6960), join the wild population annually. Despite being fed, a large proportion of released ducklings does not survive until the hunting season. Early releases may maximize pre-hunting survival. Repeated releases may prolong hunting opportunities and increase hunting bags.

Population Genetics of a Translocated Population of Mottled Ducks and Allies

“…Being under artificial selection for desired domestic traits (e.g., breeding propensity), all domestic mallards differ in fertility, overall morphology, and biology from their wild counterparts (Miller 1977, Paulke and Haase 1978, Söderquist et al 2013, Svobodová et al 2020). The movement of their genetic variation and associated maladaptive traits into wild populations may reduce survival and fecundity of wild mottled ducks (Söderquist et al 2014, McFarlane and Pemberton 2019, Svobodová et al 2020, Söderquist et al 2021. Feral mallards now pose a genetic threat to global populations of wild mallard and mallard-like taxa, with confirmed feral × wild hybrid swarms in Eurasia (Söderquist et al 2014(Söderquist et al , 2017, mainland North America (Lavretsky et al 2019(Lavretsky et al , 2020, and Hawaii (Wells et al 2019), all of which show declining populations.…”

Evaluation of Nutritional Quality and Sensory Parameters of Meat from Mallard and Four Species of Wild Goose

“…Already in the 1930s, studies showed that farmed mallards had shorter migrations than their wild conspecifics [ 19 ]. Later studies corroborated shorter migrations and movements of farmed mallards [ 37 , 38 , 39 ], but also lower survival [ 21 , 40 , 41 ]. Morphological differences have also been found between wild and farmed mallards.…”

The meaning of wild: Genetic and adaptive consequences from large-scale releases of domestic mallards

“…Importantly, our results contrast the general consensus among wildlife managers that game-farm mallards rarely survived long enough to leave the area they are released in, because it is evident from our findings that they survived at great enough rates to have their genetic variation readily found everywhere they were and are currently being released (Figs. 2 and 3 ; 78 ).…”