Researchers tracked black-naped swifts from eight populations and transferred eggs from the Netherlands to nests in Sweden. The offspring arrived in an intermediate zone in Africa, a finding that shows that both heredity and breeding environment determine the destination of migration
Billions of migratory birds leave their breeding grounds each fall for warmer climes. Many return to almost the same spot each year. But it's not always clear how young birds, who have never made the journey, know where to fly.
In geese and other social species, the young can learn the way from their parents or flock members. In contrast, songbirds Many migrate alone and at night. They also set out on their journey after their parents have already left. Therefore, the researchers sought to find out what factors direct them to their destination.
The study focused on the black-necked shrike, whose scientific name is Ficedula hypoleucaIt is a small songbird weighing about 12 grams. Its populations nest throughout Europe and Siberia, and in winter they stay inAfrica Sub-Saharan Africa.
Eight populations on the way to Africa
A large team of European researchers tracked swifts from eight breeding grounds, from Spain to Siberia. The researchers attached tiny data loggers based on light measurements to the birds. The data allowed them to reconstruct migration routes and breeding areas.
The results showed that all populations first headed to Spain and Portugal. There they stopped for a period of time. The birds then set off on a continuous flight of about 40 hours over the Atlantic Ocean, until they reached West Africa.
From this point the birds turned east, but each population travelled a different distance. The Spanish-nesting swifts remained in the westernmost part of the range. In contrast, birds from Siberia continued east as far as Nigeria.
The differences in distance were great. The Spanish population moved about 3,000 kilometers in the fall. The Siberian abductees moved almost 13 kilometers, because they also first flew westward toward Spain and Portugal.
“It is surprising that the abductions from Siberia are making such a big detour,” said researcher Kusia Lammers ofUniversity of GroningenAccording to her, a route through Italy, the Mediterranean Sea, and the Sahara Desert could have saved them about 4,500 kilometers.
The black-necked swift's relative, the white-necked swift, does indeed use the shorter route. The researchers therefore suggest that the detour is an evolutionary relic from the ice ages, when the black-necked swift's range was more restricted to western Europe and western Africa.
Dutch eggs in Swedish nests
Tracking migration routes alone cannot separate the influence of heredity from the influence of the environment. So the researchers conducted an unusual field experiment.
They collected eggs from female ostriches from the Netherlands and transported them to southern Sweden. There, the chicks hatched and were raised by Swedish adoptive parents. In addition, the researchers transported Dutch females to Sweden. Their offspring were of mixed Dutch and Swedish descent.
The team then followed the migration routes of the different groups. The Dutch robins that grew up in the Netherlands arrived in the winter in an area about 500 kilometers east of the Swedish population.
In contrast, birds hatched from Dutch eggs but raised in Sweden reached an intermediate zone. Their destination was roughly halfway between the Dutch and Swedish breeding zones. The mixed offspring also reached an area between the two destinations, but slightly closer to the Swedish destination.
Not just a genetic compass
The results show that genes alone do not determine the site of exacerbation. The early developmental environment also influences the target. However, the environment does not erase the hereditary influence. Instead, the two factors work together.
The researchers also found that all populations used a similar route for the first part of the journey. Therefore, they believe that the birds do not necessarily inherit a unique migratory direction for each population. It is possible that the important hereditary factor is actually the length of the journey or the duration of the flight.
According to Lammers, “There is probably no distinct direction of migration that is inherited in each region. Instead, the length of the path may be the constant factor.”
The possibility that the young learn the route from their parents does not fit the results. Young female raptors migrate later than adults. Therefore, they do not follow their parents during the first journey.
Implications for climate change adaptation
The findings are also important for understanding the response of migratory birds toClimate changeGlobal warming is changing the timing of spring, food availability and conditions in nesting areas, so birds may need to bring their return from Africa forward.
However, the ability to emerge early also depends on where they spend the winter and the conditions there. Different populations of the same species may therefore respond to climate change in different ways.
The experiment also shows that new combinations of nesting areas and roosting sites can emerge. The Dutch birds that bred in Sweden did not return exactly to the destination of one of the two populations. Instead, they created a new migration pattern that lies in between.
The study was led by Kusia Lammers and Jana Evhand from the University of Groningen, supervised by Prof. Christian Booth, and with the participation of a European team of researchers. The findings were published in the journal Science.
Questions and Answers:
How did the researchers track the birds?
They attached tiny data loggers to them that measured the cycles of light and darkness. This made it possible to estimate their location during migration and reconstruct their route.
What is the main innovation in the research?
The researchers didn't stop at just monitoring. They transported Dutch eggs to Sweden and raised the chicks with foster parents. The experiment made it possible to partially separate the influence of genes from the influence of the growing environment.
Do birds learn the route from their parents?
Probably not. The young migrate later than the adults and therefore do not accompany their parents. The findings indicate a combination of hereditary and environmental factors.
Why are the abductions from Siberia taking a big detour?
Researchers speculate that this is an evolutionary remnant from the ice ages, when the species' distribution was more westerly. The route has been preserved even though there is now a shorter route to Africa.
How is the research related to climate change?
The location of the outbreak affects the bird's ability to change the timing of its spring migration. Therefore, understanding the factors that determine the destination is important for predicting the adaptive capacity of different populations.
The scientific article 10.1126/science.ads0532
For the original publication: Opening the original publication
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