Spring arrival of the common cuckoo at breeding grounds is strongly determined by environmental conditions in tropical Africa

Abstract

Failure to adapt migration timing to changes in environmental conditions along migration routes and at breeding locations can result in mismatches across trophic levels, as occurs between the brood parasitic common cuckoo Cuculus canorus and its hosts. Using satellite tracking data from 87 male cuckoos across 11 years, we evaluate why the cuckoo has not advanced its arrival to the UK. Across years, breeding ground arrival was primarily determined by timing of departure from stopover in West Africa before northward crossing of the Sahara. Together with high population synchrony and low apparent endogenous control of this event, this suggests that a seasonal ecological constraint operating here limits overall variation in breeding grounds arrival, although this event was itself influenced by carry-over from timing of arrival into tropical Africa. Between-year variation within individuals was, in contrast, mostly determined by northward migration through Europe, probably due to weather conditions. We find evidence of increased mortality risk for (a) early birds following migration periods positively impacting breeding grounds arrival, and (b) late birds, possibly suffering energy limitation, after departure from the breeding grounds. These results help identify areas where demands of responding to global change can potentially be alleviated by improving stopover quality.

Explaining and predicting animal migration under global change

“…Finally, survival rates were 4.1% lower in the reduced‐NDVI SAMM (92.3%) than in the original SAMM (96.4%). Newly published analyses of cuckoo migration highlight the importance of conditions in West Africa as a constraint on spring migration to the UK (Davies et al., 2023), further validating the inference from our SAMM. This type of simulation could be produced for other threats or management scenarios.…”

Climate change is associated with asynchrony in arrival between two sympatric cuckoos and both host arrival and prey emergence

“…Temporal asynchrony in cuckoo-host arrival may result from decoupling departure signals between wintering and breeding grounds. The onset of migration in long-distance migrants may be controlled mainly by internal mechanisms [54][55][56][57] but birds can also use external environmental cues in wintering grounds and along migration routes to adjust migration timing accordingly [52,[57][58][59]. However, the observed temporal asynchrony suggests that the cuckoo's ability to follow changing climate is constrained.…”

“…Spring arrival of common cuckoos is strongly determined by environmental conditions in their wintering grounds [ 44 ]; however, we could not test this directly in our study system because information on local cuckoos' population migratory routes and wintering grounds is lacking. Cuckoo arrival is highly synchronous within a population but still may be under endogenous control, suggesting that various ecological and physiological constraints limit variation in the timing of this event in cuckoos [ 52 , 53 ]. As a result, we found evidence that differential shifts in arrival dates between cuckoos and their hosts and date of prey emergence may lead to increased temporal mismatch with their host and prey spring phenology, which may have serious consequences on cuckoo, host and prey fitness and population dynamics.…”

Combining remote sensing and tracking data to quantify species' cumulative exposure to anthropogenic change

“…Long‐distance migratory species are experiencing particularly severe population declines (Gregory et al, 2023 ; Laaksonen & Lehikoinen, 2013 ; Robbins et al, 1989 ; Rosenberg et al, 2019 ; Sanderson et al, 2006 ; Vickery et al, 2014 ; Yong et al, 2015 ), potentially because their reliance on spatially disparate seasonal resources increases their risk of encountering anthropogenic changes across the annual cycle (Newton, 2010 ; Robinson et al, 2009 ) and/or that migration may reduce the capacity for species to adapt to changing conditions on the breeding grounds (Flack et al, 2022 ; Møller et al, 2008 ). Recent research paints a complex picture regarding the importance of factors across seasonal stages, with different studies finding strong effects of wintering conditions (Adams et al, 2014 ; Davies et al, 2023 ; Kramer et al, 2018 ; Ockendon et al, 2012 , 2014 ), breeding conditions (Morrison et al, 2013 ; Ockendon et al, 2013 ), and migratory conditions (Hewson et al, 2016 ; Lisovski et al, 2021 ; Studds et al, 2017 ), and we still lack sufficient understanding to confidently pinpoint and mitigate the key drivers of population declines among many migratory species.…”

“…Remote‐sensed data has revolutionised our capacity to undertake large‐scale mapping of anthropogenic change, in particular by facilitating the assessment and combination of multiple impacts (Buchan et al, 2022b ; Halpern et al, 2008 ; Kennedy et al, 2019 ; Venter et al, 2016 ). At the same time, high‐resolution tracking data has transformed our understanding of individual‐level movements, yielding novel insights on migratory routes and timings (Davies et al, 2023 ; Hewson et al, 2016 ; van Bemmelen et al, 2019 ; Vansteelant et al, 2023 ), local movements (Shamoun‐Baranes et al, 2017 ), and survival (Buechley et al, 2021 ; Klaassen et al, 2014 ). To our knowledge, however, no studies have combined these two advances to measure year‐round individual exposure to remote‐sensed variables of anthropogenic change.…”