Blue tit grooming in spring
Blue tit movements over Lista
Skye-blue hood, black mask and yellow-breasted, small and aggressive. Blue tit is a well-known bird for many, and bird ringers are well familiar with the strength that lies in a blue tit bill. After a day of ringing blue tits, fingers can be quite sore. A substantial movement of blue tits crosses Lista each autumn, and here we take a closer look at what characterizes this movement.
Fig. 1: Blue tits 1990-2013
The figure shows the number of blue tits during autumn mist netting campaign.
Fig. 2: Timing of autumn migration
The figure shows at what time most blue tits are mist netted at Lista. The vertical axis is number of blue tits per day (averaged over 24 seasons).
Fig. 3: Controls of Lista-ringed blue tits
The map shows where Lista-ringed blue tits during 2012 and 2013 were controlled.
By M. Wold
Blue tit is one of the species we ring most of at Lista Bird Observatory, on average 1000 individuals per autumn. Almost every blue tit ringed in the autumn is a young bird hatched in the summer the same year. Figure 1 shows the number of blue tits in autumn mist netting campaigns since 1990, and the period 2010-2012 stands out from the rest with high numbers three years in a row (1700-1800 in 2010 and 2012, and >2000 in 2011). The years 2010 and 2011 were especially good, and a mild winter 2011/2012 contributed to a high survival rate for an already large population, which again gave a good breeding season in 2012, the third year in a row.
Blue tit is a species that moves around during autumn. They form flocks and wanders over relatively large distances in their search for food, about 200 km on average. But they rarely cross the ocean. Here in Scandinavia substantial movements of blue tits happen during the last part of September and during the first couple of weeks in October, and in some years the movements are invasion-like with record numbers on the move, as shown e.g. by numbers from Lista Bird Observatory. The time in the autumn when most blue tits are passing Lista can be read off Figure 2 on the right-hand side. The figure shows the distribution of blue tits from mist netting, and the last part of September and the first two weeks of October can be seen to form the peak of the distribution. However, the rest of October mist netting can also contain large numbers of blue tits.
Where to they go?All blue tits ringed at Lista in the autumn, where do they go? If one of "our" blue tits are caught again somewhere else, or is found in other ways, we receive information from Stavanger Ringing Central, and gathering this data can help form a geographical picture of the movements.
Given the large number of blue tits ringed during the three-year period mentioned above, chances increase that some are controlled at other sites. Here we are looking only at controls we have recently received, from 2012 and 2013. These control readings were mostly done at other bird observatories and at other places where mist nets are used, especially in Rogaland and Hordaland counties. For blue tits ringed in 2012 and 2013 (at Lista) we have received control readings of 33 individuals; 28 from 2012 and five so far from 2013.
The places where these control readings were made are marked on the map in Fig. 3. The map shows mainly that the movement of blue tits from Lista go northwest along the coast, to Rogaland and Hordaland. Usually the controls of Lista-ringed blue tits in these two counties happen from a few days to a couple of weeks after being ringed at Lista. On average, blue tits move 20 km per day during autumn migration. From the controls made in 2012 and 2013, seven were done by our colleagues at Revtangen ornitologiske stasjon, and six at Utsira Bird Observatory.
But not all individuals are controlled in Rogaland and Hordaland. One bird ringed at Lista on September 26th 2012 were controlled at Starene field station in Hedmark on October 25th, a month after. This blue tit has moved North-East, as opposed to most others, although it might still have followed the others through Rogaland and Hordaland first.
Some of the Northernmost controls made in 2012 and 2013 are from Herdla Fort, Askøy. No controls were made North of Hordaland. Most likely will many of the blue tits passing by Lista in the autumn winter over in Hordaland. One individual ringed at Lista on Oct 10 2012 were controlled on Nov 4 the same year on Askøy, and twice again at the same place during the winter 2012/2013, hence this individual seems to have spent the winter there. Blue tits are relatively faithful to their wintering site where they form winter flocks with great tits and are common guests in gardens with bird feeders.
Blue tit is a species that can change diet when winter comes and survive on a vegetative diet containing nuts and seeds. But when spring and summer comes, and they go through the energy-demanding breeding season, they prefer a more protein-rich diet containing caterpillars and spiders. To raise a clutch of chicks, a blue tit can catch up 20,000 caterpillars, hence it will prefer to nest in the forest.
From where do they come?Blue tits moving past Lista in the autumn, where do they come from? Among the many individuals caught in the mist netting from 2012 and 2013, six were ringed at other sites. Among these were two ringed as chicks in Mandal and Lillesand in June, and two controlled at Lindesnes a few days before passing Lista. Two other were controlled at Jomfruland and Larvik before reaching Lista.
Many blue tits moving past Lista seem to follow the Southern coastline. Perhaps many are hatched in forests in Southern Norway, but some probably also come from places further East, at least during years when young birds are forced out on long journeys in their search food, perhaps as a result of food shortage in their more local regions.
Do they return?Some migrating species return to the site where they were hatched in order to breed themselves, but do blue tits do this? In order to examine this question, it is instructive to look at controls of Lista-ringed blue tits done during spring the year after passing by Lista on autumn migration.
In the data set we are examining here, a few such spring controls were done South of Hordaland: One in Åna-Sira, one in Lyngdal and one in Lindesnes (in March). One individual were also controlled in early April at Nidingen Bird Observatory South of Gothenburg at the West coast of Sweden. It seems that there are few such spring controls being made in Hordaland and Rogaland, and that instead such controls are more common further South. Perhaps this indicates that blue tits that have survived autumn migration and the winter in Hordaland, move South again during late winter/early spring.
Foreign controlsBlue tits rarely cross Skagerrak or larger stretches of ocean, but it may still occur. Usually foreign controls of Norwegian blue tits do not go further than Denmark, and the map in Fig. 3 shows we had two controls in Denmark of Lista-ringed blue tits during 2012-2013; one at Thisted and one at Fanø, about 4-6 weeks after being ringed at Lista. But more Southern controls than this can occur.
Recently, we received information about a control made in the Netherlands by an individual ringed at Lista on Oct 1 2013. I was controlled twice, on Oct 12 and 21 the same year, at Wageningen Vogeltrekstation, Vlieland. This is one of the Southernmost controls made by a Norwegian-ringed blue tit, as the Norwegian Ringing Atlas mentions just two birds previously controlled in the Netherlands and in the Southern parts of Great Britain.
The most surprising control by a Norwegian-ringed blue tit on autumn migration was done on Shetland in 2012. Blue tit observations on Shetland are rare, and it is also rare that blue tits move that far out across the ocean. This individual blue tit was ringed at Lista on Oct 5 and controlled on Shetland, 494 km from Lista, 12 days after. Migration watches at Lista show that flocks of blue tits flying out to sea, usually returns as the danger of continuing would be too great. This individual must have lost its course, and thereafter not been capable of returning because of strong Easterly winds. Falsterbo Bird Observatory reported this autumn also of unusual behavior among blue tits, as they were seen flying out to sea against the wind, probably driven by lack of food (Kjellén 2012).
Do not live longIn addition to documenting important migration flyways and wintering areas, ringing recoveries and controls also show that the common age for a blue tit is three years. The Norwegian record is 6 years and 9 months, whereas the British Trust for Ornithology (BTO) has a documented case of a blue tit that became 9 years and 9 months old.
ReferencesBakken, Runde & Tjørve, 2006, Norsk Ringmerkingsatlas. Vol. 2. Stavanger Museum, Stavanger. 446s.
BTO Web pages
Kjellén, 2012. Sträckfågelräkningar vid Falsterbo hösten 2012. Meddelande nr. 274, Falsterbo
Wold, Røer, Kristiansen, Nordsteien, Øien, Aarvak, 2014. Bestandsovervåking ved Jomfruland og Lista fuglestasjoner i 2012. NOF-Rapport 2-2014, 33s.
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