Linking Population Declines with Diet Quality in Vaux's Swifts

Parallel declines in abundance of insects and insectivorous birds in Denmark over 22 years

“…There are few long‐term studies of insects (Taylor, is an exception). A number of studies of insects have suggested population declines by more than 75% in recent decades (Hallmann, Foppen, Turnhout, Kroon, & Jongejans, ; Hallmann et al, ; Nebel, Mills, McCracken, & Taylor, ; Nocera et al, ; Pomfret et al, ; Vogel, ). Studies of arthropod abundance in the tropics have precipitated a trophic bottom‐up cascade with effects on lizards, frogs, and birds (Lister & Garcia, ).…”

“…Humans commonly change the abundance, biodiversity, and food availability for many organisms through effects on agriculture, forestry, aquaculture, and fisheries. Recent studies have shown a reduced abundance of insects associated with the amount and the kind of pesticides used in agriculture (Nocera et al, ; Pomfret, Nocera, Kyser, & Reudink, ; Poulin, Lefebvre, & Paz, ). There have been changes in composition of the diet of insectivores as revealed by the content of dichloro‐diphenyl‐trichloroethane in historical samples of insects exploited by insectivorous birds (Nocera et al, ).…”

Stable Isotopes from Museum Specimens May Provide Evidence of Long-Term Change in the Trophic Ecology of a Migratory Aerial Insectivore

“…For aerial insectivores, a significant change in dietary isotopes of whip-poor-wills over the past 130 years adds to the mounting evidence that population declines for many of these species may be related to changes in food supply. Insect abundance has previously been shown to predict both the presence and abundance of whip-poorwills and bats (Wickramasinghe et al, 2004;English et al, 2017b) and changes in insect prey species composition appear correlated with population declines in two species of swift (Nocera et al, 2012;Pomfret et al, 2014). We believe that analysis of temporal trends in stable isotope ratios of other aerial insectivores, and further exploration of potential shifts in terrestrial baselines, will be crucial to assessing the relative importance of diet to the population trajectories of this guild.…”

“…Beetle taxa are more likely to belong to higher tropic-levels than moths (Bennett and Hobson, 2009), and the proportion of beetles relative to other insect groups found in swift (Chaetura spp.) guano accumulated in chimneys has declined in recent decades (Nocera et al, 2012;Pomfret et al, 2014). Whip-poor-wills breed throughout much of eastern North America and winter in the Florida panhandle southwards throughout most of Central America.…”

Quantifying rapidly declining abundance of insects in Europe using a paired experimental design

“…The general cause of these dramatic reductions in insect abundance remains poorly understood, although Sánchez-Bayo and Wyckhuys (2019) have made an exhaustive compilation of potential drivers that included land-use, pesticides, biological factors that include parasites and pathogens and climate change. Several studies have suggested that an important cause for such declines of insects is intensified land-use (Fox et al, 2014;Møller, 1980Møller, , 1983Møller, , 2001Sánchez-Bayo & Wyckhuys, 2019), while others have emphasized the importance of pesticide use (Hallmann, Foppen, Turnhout, Kroon, & Jongejans, 2014;Hofmann et al, 2018;Møller, 1980Møller, , 1983Pomfret, Nocera, Kyser, & Reudink, 2000;Sánchez-Bayo & Wyckhuys, 2019).…”