Changes in Sahelian bird biodiversity and tree density over a five‐year period in northern Nigeria

Stevens, Matthew; Sheehan, Danaë K.; Wilson, Jeremy D.; Buchanan, Graeme M.; Cresswell, Will

doi:10.1080/00063650903469514

Cited by 13 publications

(14 citation statements)

References 34 publications

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“…Several other studies have compared population densities between forest and farmland. Some studies find species specific differences in the effect of deforestation (Cresswell et al 2007, Stevens et al 2010). Wilson and Cresswell (2006) found only weak negative trends with tree density, and suggest that migrants are more robust than residents to habitat degradation.…”

Section: Discussionmentioning

confidence: 99%

“…Such practices reduce tree density, average tree height and likely also tree species diversity, but might provide suitable habitat for some migrants. Studies in the Afrotropics have reported mixed responses to a lower tree density among migratory species (Wilson and Cresswell 2006, Cresswell et al 2007, Stevens et al 2010). These range from large declines after conversion into farmland, to a subtle positive effect.…”

Section: Introductionmentioning

confidence: 99%

“…Previous studies have focused on the distributions and densities of Afro-Palearctic migrants in different degrees of deforestation on their West African winter grounds (e.g. Jones et al 1996, Creswell et al 2007, Stevens et al 2010). Here, we look at the interplay between local-scale spatial behaviour and different habitats as well as how this relates to bird densities in a tropical dry forest and a nearby converted farmland area.…”

Section: Introductionmentioning

confidence: 99%

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Spatial behaviour and density of three species of long-distance migrants wintering in a disturbed and non-disturbed woodland in northern Ghana

Willemoes

Tøttrup

Lerche‐Jørgensen

et al. 2017

Bird Conservation International

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SummaryChanges in land-use and climate are threatening migratory animals worldwide. In birds, declines have been widely documented in long-distance migrants. However, reasons remain poorly understood due to a lack of basic information regarding migratory birds’ ecology in their non-breeding areas and the effects of current environmental pressures there. We studied bird densities, spatial and territorial behaviour and habitat preference in two different habitat types in northern Ghana, West Africa. We study three common Eurasian-African songbirds (Willow Warbler Phylloscopus trochilus, Melodious Warbler Hippolais polyglotta and Pied Flycatcher Ficedula hypoleuca) in a forested site, heavily disturbed by agricultural activities, and a forest reserve with no agriculture. The three species differed in non-breeding spatial strategies, with Willow Warblers having larger home ranges and being non-territorial. Home ranges (kernel density) of the three species were on average 1.5–4 times larger in the disturbed site than in the undisturbed site. Much of the birds’ tree species selection was explained by their preference for tall trees, but all species favoured trees of the genus Acacia. The overall larger home ranges in the disturbed site were presumably caused by the lower density of tall trees. Density of Pied Flycatchers was 24% lower in disturbed habitat (not significantly different from undisturbed) but Willow Warbler density in the disturbed habitat was more than 2.5 times the density in undisturbed. This suggests that the disturbed habitat was less suitable for Pied Flycatcher but not for Willow Warbler. This difference is possibly related to differences in tree species preferences and suggests that at least for some species, presence of preferred tree species is more important than overall tree abundance. Such information is crucial for predicting consequences of habitat changes on larger scales and population levels, as well as for planning potentially migrant-friendly farming practices.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Spatial behaviour and density of three species of long-distance migrants wintering in a disturbed and non-disturbed woodland in northern Ghana

Willemoes

Tøttrup

Lerche‐Jørgensen

et al. 2017

Bird Conservation International

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“…, , Stevens et al . ). Nevertheless, Whinchats may benefit from anthropogenic habitat change on their wintering grounds and this therefore seems unlikely to have caused the population declines of this species observed in Europe.…”

Section: Discussionmentioning

confidence: 97%

“…In light of this, potential management options for Whinchat populations could include the encouragement of activities that increase herbaceous vegetation growth, such as leaving land fallow or greater conversion of thick scrub land to cereal crops. However, the conversion of scrub and savanna to open, intensive farming, including the removal of trees, whilst potentially beneficial for Whinchats, may be harmful for the greater number of species which select more wooded habitats (Cresswell et al 2007, Stevens et al 2010. Nevertheless, Whinchats may benefit from anthropogenic habitat change on their wintering grounds and this therefore seems unlikely to have caused the population declines of this species observed in Europe.…”

Section: Discussionmentioning

confidence: 99%

Density and behaviour ofWhinchatsSaxicola rubetraonAfrican farmland suggest that winter habitat conditions do not limitEuropean breeding populations

Hulme

Cresswell

2012

Ibis

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The Whinchat Saxicola rubetra is an Afro‐Palaearctic migrant undergoing widespread population decline. Whinchats winter in West Africa but there are almost no data on their habitat use and behaviour there that may help to explain the cause of this decline. We measured the density of Whinchats, the habitat characteristics associated with their occurrence on farmland, and the relationships between behavioural and habitat variation on farmland around Jos, central Nigeria, over three winters. Whinchats occurred in many fields harvested in the dry season, the density at three sites varying from 0.03 to 0.43 birds/ha, but they were absent at a fourth site. Whinchats were less likely to be found in farmland without particular crops (e.g. structural stem crops such as maize and millet), with more trees, lower amounts of short vegetation (grass, weeds, crops and crop stubble less than 10 cm in height), and higher amounts of medium vegetation (coverage of vegetation 10–100 cm in height) and litter (dead, unburned, vegetation on the ground). Whinchat abundance in areas of farmland where they were present was independent of most variables considered, but density was higher where there was more short vegetation cover. Foraging behaviour did not vary significantly between farmland habitats. All predictors were consistent between season, years and across sites. The presence/absence model was very poor at predicting presence and there were no strong predictors of abundance or foraging variation. This is consistent with a species well below carrying capacity within its environment so that many suitable areas do not have birds present and there is little aggregation at better sites. Overall, Whinchats were abundant and appeared to have plentiful habitat; densities have probably increased alongside the intensification of agriculture (presence of fallow farmland, short vegetation and structural crops). The results suggest that West African farmland in the dry season can support large numbers of Whinchats and that recent population declines in Europe are unlikely to be caused primarily by lack of suitable wintering habitat.

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Use of habitats by resident and migrant birds in and around a golf course on the Atlantic coast of Morocco

Greig-Smith¹

2014

Bird Study

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Changes in Sahelian bird biodiversity and tree density over a five‐year period in northern Nigeria

Cited by 13 publications

References 34 publications

Spatial behaviour and density of three species of long-distance migrants wintering in a disturbed and non-disturbed woodland in northern Ghana

Spatial behaviour and density of three species of long-distance migrants wintering in a disturbed and non-disturbed woodland in northern Ghana

Density and behaviour ofWhinchatsSaxicola rubetraonAfrican farmland suggest that winter habitat conditions do not limitEuropean breeding populations

Use of habitats by resident and migrant birds in and around a golf course on the Atlantic coast of Morocco

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