BILL NAYLOR pens a personal appreciation of this lovely finch and explains why its sperm count is unfortunately so low
AMONG the six species of bullfinch, the Eurasian bullfinch (Pyrrhula pyrrhula) is by far the most well-known, and is popular with aviculturists in many countries.
Ten subspecies range across Europe, Asia and Japan. The largest and arguably most handsome, the northern bullfinch (P.p. pyrrhula), has been kept in the UK for more than 100 years and is the most migratory, visiting Britain annually.
An old country name for our resident bullfinch (P. p. pileata) is budfinch, as it is the only British finch to be classed as an agricultural pest. Possessing a longer gut than other finches, it can digest tree buds and eats more of these than any other small European bird.
In a foliaged aviary the effects will soon be seen. In the wild, however, it mostly feeds on seeding woodland plants, including violets, nettles, buttercups, dandelion, fat hen, privet, docks, bramble, birch and beech. In Scotland, heather seeds are an important food.
In autumn, when plant seeds are scarce, it feeds almost entirely on ash keys. Laboratory tests have proved that trees with the highest fat content are selected, and that when these run low, bullfinches switch to tree buds.
Carophyll Red is usually added to captive bullfinch food, to avoid the faded pink look that used to occur with some individuals. Berries eaten by wild bullfinches include rowan (Sorbus), which contain carotenoids that colour the feathers. The northern bullfinch is more dependent on rowan berries and when the berries are scarce, it will migrate in search of them.
Bullfinches are very discerning in their predation of fruit trees, and varieties of eating apples are attacked before cooking apples. In Shropshire the bullfinch is sometimes called the plum bird.
In spring it will feed on hawthorn and other early flowering shrubs such as Forsythia, and appreciates budding sprigs of these plants in captivity. Sunflower hearts will often entice bullfinches to a bird table.
In captivity a sedentary lifestyle, combined with over indulgence on seeds can turn bullfinches into “perch potatoes”. Oil-rich seeds including sunflower, hemp and safflower are believed to shorten their lives, and bring on “gapes”, or “gasping” – terms used to describe wheezing associated with obesity.
Most bullfinches are now kept in cages or small flights, and monitoring their diet is important. Bullfinches are notoriously short-lived compared with similar sized finches – five years seems to be the average, although 17 years has been recorded. This suggests that changes to their husbandry may increase longevity.
Wild bullfinches seek dense cover to nest, preferring blackthorn and hawthorn, while generations have been bred in captivity with minimum or even absence of nest cover. Baskets are often provided, because bullfinches’ nest-building ability seems to have waned with domestication.
In the wild when breeding, no territorial behaviour is evident, but captive pairs require separate housing – two males will fight to the death. Bullfinches nest from May to July and earlier attempts in captivity are usually failures.
The four-to-six blue eggs are incubated by the hen for 12-14 days, and fledging takes place at 16-18 days.
In the wild nestlings are initially fed caterpillars, small snails and spiders, with seed being included late. In captivity young have been reared entirely on eggfood, although mini-mealworms are often provided.
The bullfinch’s call is a single plaintive piping sound, uttered loudest when single birds are trying to contact a mate or a colleague. Its other calls have been compared to a squeaky wheelbarrow. Yet for a bird with no natural song, when hand-reared before it fledges, it can be taught to sing a variety of short tunes.
The northern bullfinch is frequently said to have a distinguishing trumpeting contact call. But this only occurs in specific populations in Finland, and came to general attention in 2004 when some of these Finnish bullfinches migrated south.
Bullfinches have the smallest testes of any passerine, which may sound the kind of information only of value in a pub quiz, but it explains why a male bullfinch cannot be used in hybridisation. Similar sized passerines that are promiscuous, have much larger testes, and consequently produce more sperm.
The bullfinch is completely faithful to his mate and his low sperm count is sufficient for his needs, but insufficient to surmount the species barrier and father hybrids.
Did you know?
A cottage industry of singing bullfinches taught with the aid of a flute or whistle sprang up in Germany, and then failed.
The birds were imprinted on men, via their male singing tutors, but when sold to women they refused to perform.
Bullfinches are also known to imitate human speech. In 2004 a national newspaper ran a story of “Butch,” a hand-reared wild bullfinch who could repeat on cue, the phrase, “Who’s a pretty boy.” (Daily Mail, February 12, 2004).
Bill Naylor has enjoyed a 40-year career in ornithology and aviculture.