Why do many pheasants released in the UK die, and how can we best reduce their natural mortality?

Abstract

Around 60% of pheasants released for shooting in the UK, an estimated 21 million birds, do not end up at their intended fate: being shot. This constitutes wastage, raising economic, environmental and ethical questions. We review what is known of the fates of released pheasants and consider why they do not directly contribute to the numbers harvested. We focus on four main explanations: predation, disease, starvation and dispersal, and highlight other important causes of mortality. For each explanation, we attempt to attribute levels of loss and identify timings or conditions when such losses may be heaviest. We review factors that exacerbate losses and methods available to mitigate them. Opportunities for amelioration may arise at all stages of the rearing and release of pheasants and involve changes to the conditions under which eggs are produced, the way young pheasants are reared or the management of the environment into which they are released. We found few studies investigating impacts of post-release management techniques on pheasant survival outside of the breeding season within a UK context. We found that a number of less commonly deployed practices focusing on early-life, pre-release management may improve survival. Given the scale of pheasant releasing in the UK, even improvements in survival of 1% would mean that~350,000 fewer birds die of natural causes. Complementing current post-release management with proven novel pre-release management interventions could reduce the number of pheasants required for release, whilst maintaining current shooting levels. Lowering release numbers would lower financial costs, benefit the environment and reduce some ethical concerns over the release and shooting of reared pheasants.

Associations between gamebird releases and generalist predators

“…A more recent estimate based on the National Gamebag Census (Aebischer, ) puts the figure for non‐native gamebird releases at 50 million birds (Roos et al, ). Fewer than half of the released birds are shot (Bicknell et al, ; Madden et al, ) and the gap between numbers released and numbers shot is increasing, leading to a surplus of over 20 million pheasants in 2005 (Larkman et al, ; Robertson et al, ). These surplus birds are predated or scavenged before or during the shooting season (36% in a large study in southern England; Sage et al, ), or survive to be predated in the breeding season, or to breed (Sage et al, ).…”

“…When large quantities of birds are released, these are likely to dominate naturalized populations numerically, therefore, free‐roaming gamebird densities will be higher near release sites because gamebirds are sedentary and management is designed to retain birds (Madden, Hall, & Whiteside, ; Robertson, Woodburn, & Hill, ). In the case of introduced species, this is particularly marked, as free‐roaming populations are ultimately descended from captive stock (Robertson et al, ).…”

Heritability and correlations among learning and inhibitory control traits

“…General cognitive abilities (learning, memory, executive function) underpin critical behaviors, such as foraging ( Raine and Chittka 2008 ; Pasquier and Grüter 2016 ), mate choice ( Shohet and Watt 2009 ; Araya-Salas et al 2018 ), and predator avoidance ( Turner et al 2006 ). Importantly, performances in cognitive tasks have associated fitness consequences in wild populations (reproduction: [ Ashton et al 2018 ; Branch et al 2019 ; Shaw et al 2019 ]; survival: [ Maille et al 2016 ; Madden, Hall, et al 2018 ; Sonnenberg et al 2019 ; Langley et al 2020 ]). Although this variation and the associated fitness implications are indicative of the evolutionary potential of these traits, investigation into their heritable component has received little attention in behavioral ecology.…”

What is the research evidence for antibiotic resistance exposure and transmission to humans from the environment? A systematic map protocol

“…Shrimp are intensively raised in some parts of the world, and antibiotic usage is poorly regulated. Likewise, pheasants are reared on high levels of antibiotics and then released into the environment [46] Plants consumed raw pose are more likely to result in transmission of ARB from plants to humans…”