BIRDS THRIVE ON WINTER FEEDING

- The greenfinch - a success story

 

Nina Korhonen

 

Finns are proud of their bird counts, and with good reason. Reliable data have been collected about a hundred species for over 40 years. Which species are the success stories and which the losers? .

The most widely distributed bird in Finland is the energetic and inventive great tit (Parus major). It nests everywhere in Finland as a companion to humans, especially in luxuriant deciduous forests around residential areas, in parks and in yards. The great tit nests almost everywhere in Europe and in most of Asia up to the Pacific coast.

The great tit has thrived in Finland during the past century. According to surveys, its population almost tripled from the 1940s to the 1970s. Since then its population status has remained about the same. There are almost 800,000 nesting pairs in Finland annually, and when we count their young, the number of wintering great tits may rise as high as 8 million. Owing to high mortality in the wintertime, the number falls to 80,000 by the spring.

"The great tit has benefited from winter feeding and the proliferation of bird boxes," says Senior Curator Risto A. Väisänen from the Zoological Museum of the Finnish Museum of Natural History. Long cold spells during winter decimate populations, but feeding prevents any major catastrophes.

The greenfinch - a success story

The greatest success story among wintering bird species is the greenfinch (Carduelis chloris), which has spread throughout Europe, except the very northernmost regions, to North Africa and to parts of Asia. In recent years its populations have been on the increase in Finland, Sweden and Denmark, but remained stable in western parts of Europe.

The present greenfinch population is estimated at 200,000 pairs, whereas the figure in the 1950s was only 24,000 pairs. Since the greenfinch
is partially migratory and more and more greenfinches winter in Finland, the number of wintering individuals has increased more rapidly than that of nesting individuals.

The greenfinch, like so many other birds, is less inclined to migrate because of winter feeding. It particularly likes sunflower seeds, which are in abundant supply at feeding sites. Similarly, the rapid spread of the Ramanas rose and rape cultivation have benefited it: its favourite autumn feed is rose seed in urban areas and rape seed in rural areas. As the greenfinch prefers to nest in large shrubs in parks, it is not dependent on bird boxes.

Another success story according to Risto A. Väisänen is the blue tit (Parus caeruleus), which has benefited from the growing supply of nesting boxes and the eutrophication of waterways, as well as from winter feeding. Lush masses of common reed vegetation, which are an important source of food for the blue tit in the wintertime, are more common now than some decades ago.

The house sparrow declining unexpectedly

The house sparrow (Passer domesticus), which
has been reintroduced all over the world since the mid 19th century, is now one of the most widely distributed birds. The house sparrow nests throughout Finland, mostly in old wooden house areas and in densely built villages. It may even take up residence on a farm with outbuildings, as long as the setting is open enough and there are nest holes and dense shrubs for shelter, and cattle sheds, granaries or bird tables for feeding.

The house sparrow has been declining in Finland since the seventies; the fall has been almost 60% in a quarter of a century! As a result, it has recently been listed as a near threatened species. The change may have been even more radical than the statistics show, since sighting and counting have become much easier at feeding sites, where sparrows like to flock.

The house sparrow population in Finland is under 300,000 pairs, whereas a decade ago the annual average was still 400,000 pairs. Although the reason for this is not yet known, it has been thought that the decline in livestock farms is a likely factor: the house sparrow no longer has roosting places in cattle sheds, where it used to find fodder and seeds for food.

Skill and diligence in bird counts

Risto A. Väisänen's interest in birds was awakened in a nature club at school. "Good company and good instructors made me take a keen interest in birds. The first sighting I recorded was a Eurasian woodcock (Scolopax rusticola), which I saw on an excursion in Rovaniemi."

At present Väisänen keeps his hand in by taking part in surveys in southern Finland, but his favourite birding sites are found on the peatlands in his native southern Lapland. It is there he also treks the mires looking for ground animals like spiders. "One must also make bird counts in order to understand the reality of field work and to be able to process materials collected by others."

Bird counts in Finland date back 60 years. Survey data in a series this long are unique in Europe.

In winter counts, all the birds detected along the standard route are recorded by one or more birders. The counting excursion takes all the daylight hours of a winter day. Monitoring data are reported in the same form year after year from three counts: the same round is made once in late autumn, in mid-winter around the New Year, and in February-March.

The average route is about ten kilometres long. There are 500 rounds in all and about one thousand counters, all keen bird observers. The detailed statistics thus collected contain systematic information about one hundred bird species. The counters also record other data, such as the temperature, the snow cover and the rowan berry yield.

Signs of global warming

The monitoring data also allow long-term studies of the winter population trends. Birds are good indicators of climate change.

"Bird populations react strongly to the so-called greenhouse phen-omenon. As winters get warmer, some species thrive, others decline," Väisänen says.

Climate change ultimately chan-ges the composition of forest spe-cies. Deciduous trees become more common and coniferous trees decline. This means better conditions for animals which thrive in broad-leaved forests, and loss of habitat for species living in boreal taiga forests.

"Climate change is by no means an easy subject to study, because there are many factors simultane-ously affecting the size of bird populations. For instance, frequent cold winters have an immediate effect on the populations of some species. The goldcrest (Regulus regulus) may be virtually wiped out during a cold winter, but since it is partially migratory, it does not die out in Finland. Owing to its reproductive capability, the goldcrest recovers easily from winter losses," Väisänen explains.

In the mid eighties Finland had three cold winters in a row, but there were very mild periods towards the end of the nineties. Väisänen points out that changes in bird population status due to climate are seen in long sequences _ and, as we know, there is a solid data basis for it in Finland.

In the European perspective, the major single environmental change has been the emergence of intensive agriculture. Fields do not offer as many nesting places and as much food as they used to. Changes in forestry have been unfavourable to birds _ managed forests in particular are bleak habitats for sedentary birds. The building stock also influences bird populations: modern buildings offer few holes for birds to nest in.

"The success stories are species which can benefit from the food offered by humans. Winter feeding is an important factor up here in the Any bird feeder who knows the most common winter birds can become a bird counter. Risto A. Väisänen says that especially women have excelled in this: the Zoological Museum has received many meticulously completed forms.

Birds are monitored at a feeding site for about a fortnight each month from the beginning of October until the end of April. Apart from the highest number of individuals of each species, information is collected about the quality and amount of food and any mammals attracted by food offered at the feeding site. There have been sightings of 26 mammals _ about half of the winter active fauna of Finland _ the most common being the squirrel, but also hares, mice, moles and cats are frequent visitors at bird feeders.

The most numerous winter birds in residential areas are the yellowhammer (Emberiza citrinella), house sparrow, great tit, and greenfinch. The most frequent dinner guest is the great tit, which has been recorded at all the feeding sites. Altogether 110 species have been seen at feeders. ß

 

The same route for over 40 years Kimmo Aula, resident of Helsinki, could be called a bird counter extraordinaire. This biology teacher, now retired, has monitored winter birds for over 40 years, ever since such surveys started in Finland in the winter of 1956/1957. "You really look forward to autumn, because it means bird coun-ting," Aula says, flicking through his carefully recorded statistics. There are three bird counts each year: in early November, around the New Year and in late February-early March. Bird counting requires solid knowledge about birds, sharp eyes and ears, deep passion, and vigour to trek the rounds. One monitoring route is about ten kilometres, and Kimmo Aula has four of them in the Helsinki Metropolitan Area. Each year he devotes nine whole days to bird counting. At its best, bird counting offers delightful experiences in clear winter weather, but such luck is not always guaranteed. For Aula, the coldest round began in -27 degrees Celsius in the morning. Nothing much was stirring in the forest; the birds perched on boughs all fluffed up to fight the cold. The counters felt cold long after they had returned home. The chill factor near the sea also makes the counters tremble, preventing any attempts to write with bare hands. Kimmo Aula's oldest counting route goes along the shore in Lauttasaari, Helsinki. For 45 winters he has recorded the weather and the birds sighted or heard there. The number of birds varies greatly according to the weather, the ice situation and the rowan berry yield. During the best year, winter 1966, he sighted over 4,000 individual birds, whereas the winter of 1958 yielded data on only 371 birds. All in all, he has encountered about 50 species on his rounds in Lauttasaari. But even Kimmo Aula has not seen everything yet. "My aim is to see all the bird species breeding regularly in Finland, which are about 240. I'm still missing one, the red-flanked bluetail (Tarsiger cyanurus)."