Sperm head abnormalities are associated with excessive omega‐6 fatty acids in two finch species feeding on sunflower seeds

Abstract

In a rapidly changing world, it is important to understand how urban environments impact wildlife. For example, supplementary feeding of birds, though well‐intended, might have unexpected negative effects on the health of individual animals. Sunflower seeds are commonly provided in garden bird feeders, but they contain high levels of linoleic acid (LA), an omega‐6 polyunsaturated fatty acid (PUFA). Omega‐6 PUFAs are associated with increased oxidative stress, which can damage cell membranes, and in particular sperm cells. We assessed the level of LA in the blood of two seed‐eating finch species, greenfinches Chloris chloris and hawfinches Coccothraustes coccothraustes, caught in and in environments with direct access to sunflower seed feeders (Norway), and compared these with the level of LA in a smaller number of individuals sampled in in a rural area with low incidence of sunflower seed feeders (Czech Republic). Furthermore, we investigated the relationship between the proportion of LA in the blood (as well as the proportion of 10 other fatty acids) and sperm quality (the frequency of sperm head abnormalities and sperm swimming speed). We found that both finch species, but particularly greenfinches caught near feeders, exhibited levels of LA that were considerably higher than those previously reported for other wild birds. We also found that the proportion of LA was positively correlated with the frequency of abnormal sperm heads (sperm missing the acrosome), while there was no significant effect of fatty acid composition on sperm swimming speed. Our results indicate that the sperm quality of finches may be negatively affected by a high intake of sunflower seeds, adding to a growing body of research showing that supplementary feeding may have detrimental side effects for urban animals. This is particularly relevant for the greenfinch, which is currently affected by disease and population declines.

Experimentally induced flight costs do not lead to increased reliance on supplemental food in winter by a small songbird

“…Nonetheless, the findings from this study provide critical information that should inform the debate regarding policy guidelines for intentional feeding of wildlife (Reynolds et al 2017, Baverstock et al 2019). Going beyond our study, it is clear that intentional feeding can induce a diverse set of biologically relevant changes in bird populations, with some effects only recently uncovered (Bosse et al 2017, Stostad et al 2019). Therefore, additional research is needed for a comprehensive understanding of how recreational feeding influences wild, free‐ranging bird populations in areas where supplemental feeding is regularly practiced.…”

“…These include negative effects such as facilitating disease transmission (Adelman et al 2015, Becker et al 2015, Cox and Gaston 2018), enhancing competition (Rickett et al 2013), impairing breeding performance (Plummer et al 2013a, b2013b, Malpass et al 2017) and restructuring local communities (Galbraith et al 2015), as well as positive effects that include enhanced winter survival (Brittingham and Temple 1988, Danner et al 2013), body condition (Desrochers and Turcotte 2008, Wilcoxen et al 2015, Broggi et al 2021) and reproductive output (Robb et al 2008a). Furthermore, intentional feeding of wild bird populations has been found to result in changes to migration behavior (Plummer et al 2015), bill structure (Bosse et al 2017) and even the structure of gametes (Stostad et al 2019), suggesting that supplemental feeding may impact wild animal populations in ways that are not fully understood at the current time.…”

Using DNA metabarcoding to explore spatial variation in diet across European Hawfinch populations

“…Supplementary food is predominantly used by birds to enhance survival when natural food supplies are reduced (Lawson et al 2018). However, there is a risk that birds may become reliant on artificial food sources, as well as increasing disease transmission risk (Murray et al 2016, Lawson et al 2018, Støstad et al 2019. Evidence suggests that high congregation densities of birds over a prolonged period of time, coupled with poor hygiene, can result in pathogen contamination of feeding stations (Hanmer et al 2017, Lawson et al 2018.…”

Killing with kindness: Does widespread generalised provisioning of wildlife help or hinder biodiversity conservation efforts?

“…Elevated wildlife mortality rates around provisioned food may occur (Pavisse et al, 2019;Swallow et al, 2019), with predation by domestic pets as well as window collisions exacerbated by encouraging wildlife into the vicinity of human settlements (Kummer and Bayne, 2015;Pavisse et al, 2019). The reproductive success of recipients might also be negatively affected if they become dependent upon provisioned food resources of poor nutritive value (Chamberlain et al, 2009;Plummer et al, 2013), which can affect blood chemistry (Ishigame et al, 2006;Støstad et al, 2019) with unknown health impacts. Nestboxes can be associated with an increased bacterial load and egg mortality compared to natural cavities (Devaynes et al, 2018), owing to different internal microclimates.…”