One night last week, I was surprised and delighted to hear loud, mellifluous bird song at midnight.
What could be singing such colourful tunes so late at night? I recorded the sounds of two birds on neighbouring rooftops, seemingly singing a melodious duet, and played them to a birding friend who, after hearing only about three notes, told me that they were robins.
European robins (Erithacus rubecula) live throughout Europe, Russia and western Siberia and there are approximately 6 million pairs in the UK. British and Irish robins do not generally move more than 5km, the exception being adult males moving between their breeding and winter territories.
Some UK robins, mostly females, cross the Channel to spend the winter in warmer regions, in some cases travelling as far south as southern Spain and Portugal.
Our resident birds are joined by immigrants from Scandinavia, continental Europe and Russia, which come to the UK to avoid the severe winters there.
Robins are one of the few UK species that sing throughout the year and males and females sing to proclaim and defend their own individual territories. In autumn and winter both sexes occupy separate winter feeding territories and defend them with song. Adult female European robins show elevated testosterone levels in winter when they are defending feeding territories which will improve their chances of survival and of successfully raising young in the spring.
Robins are insectivorous birds that are well adapted to foraging in low light levels.
They have large eyes compared to body size which means that more light can enter their eyes. Urban robins will continue to feed under artificial light well into the night. In birds a network of brain nuclei called the song control system is responsible for song production and the size of these brain areas increases from the non-breeding to the breeding season as new neurons and synapses develop, triggered by changes in day length – or the street lights outside our house.
Around Christmas-time, robins begin to explore other robins’ territories in the hope of finding a mate and their singing becomes stronger and more passionate – it certainly was last week!
By mid-January the majority of robins will have paired up and the females stop their territorial singing. The males, however, continue to sing to declare ownership of what is now a joint future breeding territory, one which they will fight to the death to defend.
Life expectancy is just over a year and up to 10% of adult mortality is accounted for by territorial disputes.
Were the birds I heard winter visitors singing to establish territories or resident robins defending theirs?
The robin has been called Robin Redbreast since the 15th Century and in 2015 it was voted Britain’s national bird. Its association with Christmas is probably because in Victorian Britain, postmen were known as robins because of the red tunics they wore and they delivered the first Christmas cards.
Have a look - how many Christmas cards do you have which depict a robin?