Whereas knowledge of birds' breeding grounds in Europe is extensive – due to a wide network of ringing stations and research, knowledge of their wintering grounds in Africa is lacking.
In each feather, there is a 'hydrogen isotopic signature' that can indicate its growth location.
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The researchers have found that the Eurasian Blackcap, the most prevalent migrant in the Jerusalem Bird Observatory and one of the most common in Israel, arrives from Ethiopia.
The study, led by the Ph.D. student Tal Raz from The School of Zoology and The Steinhardt Museum of Natural History, Tel-Aviv University, was held in The Nili and David Jerusalem Bird Observatory and in cooperation with Environment Canada.
Millions of migratory birds fly over Israel on their way from Africa, where they spend the winter ("wintering"), to Europe and western Asia, and back. Of these, thousands of migratory songbirds stopover to rest in Jerusalem. Research conducted as part of a Master's degree, under the supervision of Dr. Takuya Iwamura, of the Ph.D. student Tal Raz of The School of Zoology and The Steinhardt Museum of Natural History, Tel-Aviv University, had aimed to identify the wintering grounds of songbirds that stopover in Jerusalem during their spring migration and answered for the first time the question: Where do five common Jerusalem migrants come from in Africa?
Whereas knowledge of birds' breeding grounds in Europe is extensive – due to a wide network of ringing stations and research, knowledge of their wintering grounds in Africa is limited. To reduce the knowledge gap for five species of songbirds that stop over during their spring migration at the Jerusalem Bird Observatory (JBO), the researchers used species distribution models and stable isotope analysis.
For each species of songbirds that stopover in Jerusalem: Eurasian Reed Warbler, Eastern Olivaceous Warbler, Eurasian Blackcap, Olive-tree Warbler, and Barred Warbler, the research created species-specific distribution models by using ~1500 observation localities of the species and environmental variables that can impact the species' distributions (rainfall, temperature, etc.), resulting in a range that represents the species suitable habitat in Africa.
To reveal the Jerusalem migrants' wintering location within the African suitability ranges, a sample collection, led by Dr. Gidon Perlman and Dr. Yosef Kiat, was conducted at the Jerusalem Bird Observatory during spring migration. One feather grown (molted) in Africa during winter was collected from ~100 individuals of each species. The missing feather did not hinder the birds from continuing their migration. In each feather, there is a 'hydrogen isotope signature' that can indicate its growth location.
Hydrogen appears in nature in two ways: light and heavy. Each place on Earth has a certain ratio of these isotopes – the light and the heavy. The researchers have compared the isotopic ratio in the birds' feathers to the occurring ratio in Africa (an existing knowledge). With this, it is possible to identify the location where the feather was grown and improve the knowledge of the wintering grounds of each of the five species. For example, the researchers discovered that the Eurasian Blackcap (one of the most common migrants in Israel) is coming from Ethiopia and near areas. Additionally, they found that Eastern Olivaceous and Eurasian Reed Warblers arrive from two regions in Africa, one in eastern Africa and the other in central Africa. They also found that early-arriving Eurasian Reed Warblers winter farther from Israel than late-arriving individuals.
This study, which identifies the wintering grounds of the studied species, will enable us in the future to understand the threats imposed on the survival of the birds in Africa and to protect them more effectively. According to the researcher, Tal Raz of The School of Zoology and The Steinhardt Museum of Natural History, Tel-Aviv University: 'Migratory species face multiple threats to their survival as they depend on several locations during migration, as opposed to residents, and deterioration of only one of those locations can cause population decline. Currently, great efforts are being made in Europe to protect migratory birds, but we need to remember that these birds spend many months each year in migration, where they are threatened by poaching, and in Africa, where habitat destruction danger their survival. To conserve these species, we have to identify key locations along their entire migration cycle, so we can estimate their threats and act to protect them.'
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