Contrasting use of space by two migratory Afro-Palearctic warblers on their African non-breeding grounds

Mostafa, Dina Abdelhafez Ali; Willemoes, Mikkel; Salewski, Volker; Ortvad, Troels Eske; Dabelsteen, Torben; Thorup, Kasper

doi:10.1007/s10336-021-01881-1

Cited by 5 publications

(8 citation statements)

References 37 publications

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“…Pied Flycatcher (Salewski et al 2003), Whinchat (Blackburn & Cresswell 2016b) and Northern Wheatear (Blackburn & Cresswell 2016c). Other migrant species have individually overlapping home ranges (Willemoes et al 2017, Mostafa et al 2021) but feed on their own and do not tolerate congeners or other species nearby, particularly species with a lower body mass (Salewski et al 2007, Zwarts et al 2023e).…”

Section: Discussionmentioning

confidence: 99%

The Fortunes of Migratory Birds from Eurasia: Being on a Tightrope in the Sahel

Zwarts¹,

Bijlsma²,

Kamp³

2023

Ardea

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Many studies have shown that rainfall in the Sahel has a great influence on population trends of European bird species that spend the northern winter there. African bird species living in the Sahel, notably those that forage on the ground, have also shown significant declines, but independent of rainfall. This paper summarises the results of field data gathered in the entire Sahel and evaluates the many factors that play a role in the fortunes of birds. (1) Rainfall determines the extent of open water in the Sahel, and by default the fortunes of waterbirds. In recent decades the surface area of open water has increased because water tables have risen. (2) Rainfall south of the Sahel determines river discharge and therefore the surface of floodplains in the Sahel. Rainfall has a cumulative effect: discharges disproportionally decrease after a number of years with little rain, and vice versa. During the dry season (October-May), floodplains gradually dry out. In wet years, water -and hence food -is available for birds up to their departure, but in dry years birds become concentrated at the few remaining pools and so present an easy target for bird-trappers. Further desiccation leads to starvation. (3) After a year with heavy rainfall, seed is available in abundance, but a dry year results in a shift in the plant community and a low seed supply. Mortality among seedeaters increases under dry conditions. (4) In dry years, trees lose their leaves early on, forcing arboreal birds into a diminishing number of trees that retain leaves. In extremely dry years trees die on a massive scale and it takes many years before tree coverage is restored. When droughts occur in quick succession, as in 1972/73 and again in 1984/85, tree recovery is slow and populations of arboreal birds will continue to decline, or recover slowly or only partly (as for Eurasian Wryneck Jynx torquilla and Common Redstart Phoenicurus phoenicurus, whose numbers remain reduced by tenfold when compared to the 1950s, despite a slight recovery). Rainfall in the Sahel gradually recovered after 1990, as did the woody vegetation albeit with a delay, and many migratory bird species responded accordingly. Subalpine Warblers Curruca subalpina and Western Orphean Warblers Curruca hortensis have increased as much as threefold to fivefold since 1990. Southern European bird species, wintering in the arid parts of southern Sahara and Sahel, were hit the hardest during the Great Drought in 1969-1992, but also recovered the fastest, particularly strongly once rainfall had significantly recovered.Despite clear links between migratory birds and rainfall-related variables in their wintering areas, a migrant's world is more complicated than exclusively being constrained by rainfall. In the past century, the human population in sub-Saharan Africa has increased tenfold, with far-reaching consequences. (1) Cattle numbers boomed and grazing pressure increased greatly. Heavy grazing means lower grass seed production, especially of seeds that birds prefer. The steep decline of gr...

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Section: Discussionmentioning

confidence: 99%

The Fortunes of Migratory Birds from Eurasia: Being on a Tightrope in the Sahel

Zwarts¹,

Bijlsma²,

Kamp³

2023

Ardea

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“…Several studies found that migrants in West African wintering areas were solitary, sedentary and territorial, e.g. in Western Olivaceous Warbler, Melodious Warbler, Common Whitethroat, Subalpine Warbler, Common Redstart and European Pied Flycatcher, in contrast to Willow Warbler and Common Chiffchaff which were recorded to be itinerant (Skilleter 1995, Sauvage et al 1998, King & Hutchinson 2001, Salewski et al 2002a, Willemoes et al 2018, Thorup et al 2019, Mostafa et al 2021, Tapia-Harris & Cresswell 2022). Territorial birds can be expected to engage more often in intraspecific agonistic encounters, especially when suitable habitat is scarce or food resources are in short supply, and in interspecific competition when foraging habitat and behaviour show overlap with those of ecologically closely related species (Brown 1964, Wilson & Cresswell 2007).…”

Section: Discussionmentioning

confidence: 99%

Frequent Agonistic Interactions among Arboreal Birds in Savannahs But Not in Humid Forests of Africa

Zwarts¹,

Bijlsma²,

Kamp³

2023

Ardea

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Arboreal birds in the Sahel are highly selective in their tree choice. Most migrant, but also resident, birds are found in a few tree species and within those species often only in trees with abundant leaves and flowers. For this reason alone, preferred trees were expected to teem with birds. This was not the case. Most bird species were present in trees as singletons, even half of the Senegal Eremomela Eremomela pusilla – the most social species of all – were recorded as solitary birds. The probability that two different bird species were in the same tree was also very small, 2.8% on average. Mixed-group foraging flocks of arboreal birds, as so often reported for tropical forests, did not occur in the Sahel. Perhaps birds forage singly because they have no need to fear the raptors that are common in the forests further south. Some species, such as European Pied Flycatcher Ficedula hypoleuca and Common Redstart Phoenicurus phoenicurus, defend winter territories, but for other species individual home ranges show overlap. In the humid forests further south, and among resident species in the Sahel, few agonistic interactions were seen, but migratory birds were often agonistic with congeners and even more frequently with birds of other species. Larger bird species usually won agonistic interactions, but Western Olivaceous Warblers Iduna opaca chased off birds twice their own body size. Subalpine Warbler Curruca iberiae + subalpina + cantillans and other Curruca species, with the exception of Lesser Whitethroat Curruca curruca, were also intolerant. Western Bonelli's Warblers Phylloscopus bonelli, and during migration also Willow Warblers Phylloscopus trochilus, were most often on the receiving end of agonistic interactions. Far fewer agonistic interactions were recorded in the more humid regions to the south of the Sahel. This disparity may hinge on the higher intra- and interspecific encounter rate in the Sahel, where a greater fraction of trees are occupied by birds, than in the humid forests.

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“…Other studies suggest differences in habitat use between ecologically similar migratory tanagers in the same habitat. 21 On an ecological scale, species can differ in the chosen vegetation level and feeding strategies. 21,49 So that their coexistence in reproductive territories can be favoured by the spatial partition on a microhabitat scale.…”

Section: Discussionmentioning

confidence: 99%

“…5,9,11 Other studies on the habitat selection dynamics of warblers considered factors such as anthropic disturbance, 19 seasonality 20 and social behaviour. 21 Finally, Coreau & Martin 22 performed a multiscale analysis in order to improve the knowledge about bird distribution and changes in their habitat selection.…”

Section: Introductionmentioning

confidence: 99%

Breeding habitat selection of three sympatric species of Mediterranean warblers in eastern Spain

Moreno-Mosquera,

Drechsler,

Rivera

et al. 2023

Avian Biology Research

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Understanding habitat selection patterns in congeneric species has raised special interest due to its importance when designing conservation strategies for the species. We analysed reproductive habitat selection of three coexisting warbler species in the eastern Iberian Peninsula. We detected the individuals by their vocalizations at 40 listening points in two study areas (Carcaixent and Alcoy). We used satellite images to identify different vegetation types and their availability. Reproductive habitat selection was analysed by the Ivlev selectivity index and a compositional analysis. In addition, we determined the effect of different habitat variables (dominant vegetation, vegetation height, cover and site) on the presence of the species fitting a binomial GLM with logistic linking function. We found that the Sardinian Warbler ( Curruca Melanocephala) selected scrub-dominated areas; while the Dartford Warbler ( C. undata) preferred areas with low (<50%) vegetation cover; and the Subalpine Warbler ( C. cantillans) was present in areas with scrubs and low (<50%) vegetation cover, avoiding crops. The compositional analysis showed that the species used different vegetation types, in relation to their availability and that the selection differed between species. The Sardinian Warbler was the only species which showed spatial variation in reproductive habitat selection. Our results evidence that the studied warbler species select and avoid different types of vegetation in relation to their specific requirements and the present habitat structure. This represents valuable information to understand the composition of local communities and the reproductive habitat selection of the studied species.

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Contrasting use of space by two migratory Afro-Palearctic warblers on their African non-breeding grounds

Cited by 5 publications

References 37 publications

The Fortunes of Migratory Birds from Eurasia: Being on a Tightrope in the Sahel

The Fortunes of Migratory Birds from Eurasia: Being on a Tightrope in the Sahel

Frequent Agonistic Interactions among Arboreal Birds in Savannahs But Not in Humid Forests of Africa

Breeding habitat selection of three sympatric species of Mediterranean warblers in eastern Spain

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