Winter spatial distribution of threatened acridivorous avian predators: Implications for their conservation in a changing landscape

Augiron, Steve; Gangloff, Benoît; Brodier, S.; Chevreux, Fabrice; Blanc, Jean-François; Pilard, Philippe; Coly, Adrien; Sonko, Abba; Schlaich, Almut E.; Bretagnolle, Vincent; Villers, Alexandre

doi:10.1016/j.jaridenv.2014.10.001

Cited by 14 publications

(18 citation statements)

References 33 publications

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“…The main study site was the area of Khelcom, also known as Mb egu e (14Á44-14Á74°N and 15Á42-15Á64°W, ca. 55 000 ha) which is the most important known wintering area of Montagu's Harriers in West Africa, harbouring over 5000 individuals (Mulli e & Gu eye 2010; Augiron et al 2015). In Khelcom, individual roosts support between several hundred up to 4000 harriers (January 2015).…”

Section: Study Sitesmentioning

confidence: 99%

“…; Augiron et al . ), thus lack the possibility to move further south when conditions continue to deteriorate during winter. From their last wintering site in the southern Sahel, birds depart directly north at the onset of spring migration (March).…”

Section: Introductionmentioning

confidence: 99%

“…During the wintering season, sites are located progressively further southwards following a shifting 'green belt' of vegetation harbouring highest food abundance (Trierweiler et al 2013). Wintering harriers prefer open landscapes and avoid forested areas (Limiñana et al 2012a;Trierweiler et al 2013;Augiron et al 2015), thus lack the possibility to move further south when conditions continue to deteriorate during winter. From their last wintering site in the southern Sahel, birds depart directly north at the onset of spring migration (March).…”

Section: Introductionmentioning

confidence: 99%

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How individual Montagu's Harriers cope with Moreau's Paradox during the Sahelian winter

Schlaich

Klaassen

Bouten

et al. 2016

Journal of Animal Ecology

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Summary 1.Hundreds of millions of Afro-Palaearctic migrants winter in the Sahel, a semi-arid belt south of the Sahara desert, where they experience deteriorating ecological conditions during their overwintering stay and have to prepare for spring migration when conditions are worst. This well-known phenomenon was first described by R.E. Moreau and is known ever since as Moreau's Paradox. However, empirical evidence of the deteriorating seasonal ecological conditions is limited and little is known on how birds respond. 2. Montagu's Harriers Circus pygargus spend 6 months of the year in their wintering areas in the Sahel. Within the wintering season, birds move gradually to the south, visiting several distinct sites to which they are site-faithful in consecutive years. At the last wintering site, birds find themselves at the southern edge of the Sahelian zone and have no other options than facing deteriorating conditions. 3. We tracked 36 Montagu's Harriers with GPS trackers to study their habitat use and behaviour during winter and collected data on the abundance of their main prey, grasshoppers, in Senegal. Since grasshopper abundance was positively related to vegetation greenness (measured as normalized difference vegetation index, NDVI), we used NDVI values as a proxy for prey abundance in areas where no field data were collected. Prey abundance (grasshopper counts and vegetation greenness) at wintering sites of Montagu's Harriers decreased during the wintering period. 4. Montagu's Harriers responded to decreasing food availability by increasing their flight time during the second half of the winter. Individuals increased flight time more in areas with stronger declines in NDVI values, suggesting that lower food abundance required more intense foraging to achieve energy requirements. The apparent consequence was that Montagu's Harriers departed later in spring when their final wintering site had lower NDVI values and presumably lower food abundance and consequently arrived later at their breeding site. 5. Our results confirmed the suggestions Moreau made 40 years ago: the late wintering period might be a bottleneck during the annual cycle with possible carry-over effects to the breeding season. Ongoing climate change with less rainfall in the Sahel region paired with increased human pressure on natural and agricultural habitats resulting in degradation and desertification is likely to make this period more demanding, which may negatively impact populations of migratory birds using the Sahel.

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Section: Study Sitesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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How individual Montagu's Harriers cope with Moreau's Paradox during the Sahelian winter

Schlaich

Klaassen

Bouten

et al. 2016

Journal of Animal Ecology

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“…Harriers breeding in western Europe spend the wintering season (October-March) in the western Sahel (Limiñana et al 2012, Trierweiler et al 2013, where they prey mostly on grasshoppers (Trierweiler and Koks 2009, Trierweiler et al 2014, Augiron et al 2015, Schlaich et al 2016. The Montagu's harrier is a long-distance migrant breeding across the open farming landscapes of the western Palearctic, from northern Morocco to western Russia and Kazakhstan.…”

Section: Introductionmentioning

confidence: 99%

“…The Montagu's harrier is a long-distance migrant breeding across the open farming landscapes of the western Palearctic, from northern Morocco to western Russia and Kazakhstan. Harriers breeding in western Europe spend the wintering season (October-March) in the western Sahel (Limiñana et al 2012, Trierweiler et al 2013, where they prey mostly on grasshoppers (Trierweiler and Koks 2009, Trierweiler et al 2014, Augiron et al 2015, Schlaich et al 2016. In France, harrier diet is mainly composed by common voles Microtus arvalis which densities strongly affect the number of breeding pairs, reproductive success and possibly survival (Millon and Bretagnolle 2008).…”

Section: Introductionmentioning

confidence: 99%

Disentangling the effects of environmental conditions on wintering and breeding grounds on age‐specific survival rates in a trans‐Saharan migratory raptor

Millon

Danovaro

Printemps³

et al. 2019

Journal of Avian Biology

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Migratory species are subject to environmental variability occurring on breeding and wintering grounds. Estimating the relative contribution of environmental factors experienced sequentially during breeding and wintering, and their potential interaction, to the variation of survival is crucial to predict population viability of migratory species. Here we investigated this issue for the Montagu's harrier Circus pygargus, a trans‐Saharan migrant. We analysed capture–recapture data from a 29‐year long monitoring of wing‐tagged offspring and adults at two study sites in France (Rochefort‐RO and Maine‐et‐Loire‐ML). The study period covers a climatic shift occurring in the Sahel with increasing rainfall following a period of droughts (Sahel greening). We found that harriers’ adult survival in RO (between 1988 and 2005) varied over time and was sensitive to the interaction between the amount of rainfall in the Sahel and the annual mean breeding success, two proxies of prey availability. The occurrence of adverse conditions on breeding and wintering grounds in the same year decreased survival from 0.70–0.77 to 0.48 ± 0.05. Juvenile survival in RO was slightly more sensitive to conditions in Europe than in the Sahel. Unexpectedly, lower survival rates were found in years with higher mean breeding success, suggesting compensatory density feedbacks may operate. By contrast, adult survival in ML, monitored between 1999 and 2017, was higher compared to RO (0.76 ± 0.03 versus 0.66 ± 0.02), remained constant and unaffected by any proxy of prey availability. This difference seems consistent with the fact that harriers in ML experienced better and especially less variable environmental conditions during breeding and wintering seasons compared to RO. Overall, we showed that survival of a migratory bird is sensitive to the level of variability in environmental conditions and that adverse conditions on wintering grounds can amplify the negative effects of conditions during the previous breeding season on birds’ survival.

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Conservation and Ecology of African Raptors

et al. 2018

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Winter spatial distribution of threatened acridivorous avian predators: Implications for their conservation in a changing landscape

Cited by 14 publications

References 33 publications

How individual Montagu's Harriers cope with Moreau's Paradox during the Sahelian winter

How individual Montagu's Harriers cope with Moreau's Paradox during the Sahelian winter

Disentangling the effects of environmental conditions on wintering and breeding grounds on age‐specific survival rates in a trans‐Saharan migratory raptor

Conservation and Ecology of African Raptors

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