Woodlands are the natural home for the birds. They are believed to be safe there. And we also assume that due to the urbanization and converting forest areas into towns, we destroy their livelihood , render them homeless and put these birds at high risk . Though that is partially true, a study now has revealed that it is birds in woods and not in towns, that is High risk for the breeding of these birds. The study iterates that the breeding of such birds are high in towns rather than in the woods.
They found that those living in urban areas were better able to cope during spells of exceptionally cold and wet weather because they were less dependent on a single food source to feed their chicks.
Birds nesting at all three sites suffered during the harsh spring of 2012, which was particularly cold and the wettest year on record, raising fewer chicks than usual with a lighter body weight than average.
But those studied at the Brampton Wood nature reserve, a site of ash, oak and maple woodland, were worse affected than those at the Cambridge University Botanical Gardens in Cambridge city centre and Cow Lane nature reserve, a riverside area of willows and reed beds.
Blue tits and great tits usually lay one egg per day until their clutch is complete and then start to incubate them, but the birds at Brampton Wood delayed their incubation in the cold weather, meaning their chicks hatched later.
Great tits were particularly badly affected, with the average span from laying the first egg to hatching lasting 32 days. The figure for birds at urban sites was 17 days.
A delay in hatching generally leads to a smaller brood, and fewer chicks leaving the nest.
Writing in the PLOS ONE journal, the researchers said this was most likely because the weather had led to a scarcity of caterpillars, a key type of prey. Those in urban areas had a wider range of other food sources with which to compensate.
Rainfall, which washes caterpillars off leaves and makes them harder for birds to find, and cold temperatures, which affect their reproduction and growth, were found to be the main factors.
Dr Nancy Harrison, one of the researchers, said: “The birds breeding in the good woodland habitat really struggled during last year’s cold, rainy spring.
“Blue tits and great tits in urban areas often forage for other prey and so are less reliant on one particular food source. These ‘urban scavengers’ were better able to cope in 2012 when these caterpillars were in short supply.”
Over the whole of the ten-year study woodland birds produced larger and healthier broods, but this may not always be the case, she added.
“The breeding season is controlled by a hierarchy of factors including daylight and temperature, with temperature playing a key role in caterpillar reproduction and growth.
“If these extreme weather events become more commonplace due to the effects of climate change, then birds living in urban environments may have the advantage.”