THE number of birds in the United States and Canada has plunged by nearly three billion over 50 years in a decline so startling, experts have declared a “full-blown crisis”.

Three billion?
It’s a drop so immense it is hard to even comprehend - 2.9 billion fewer birds than there were half a century ago, according to analysis published in the journal, Science; a report regarded as the most thorough ever attempt to understand what is happening to avian populations. It’s an estimated fall of 30 per cent in the total bird population.

How did they gauge the figures?
The new study looked at the figures for 529 bird species from long-standing ground-based surveys, in which volunteers send in bird population counts. 
The scale of the losses was also corroborated alongside weather radar data, with birds recorded on radar at more than 140 stations across the US from 2007 to last year.

What did the weather data show?
It focused on springtime and migrating birds, only to record a 14 per cent fall, in line with the other findings.

And it’s happened so fast?
The speed of the bird loss in America has staggered even the experts. 
Adriaan Dokter, a bird migration ecologist at Cornell Laboratory of Ornithology, which conducted the research, said they are fearful as all of this loss is occurring “on the timescale of one human life”.

What did the study find?
Steep losses across the board, even among typically common birds, such as sparrows, blackbirds, larks, starlings, finches and robins. 
These traditionally abundant birds are vital to the survival of ecosystems, from pollinating flowers to controlling pests, and their disappearance is sure to wield a massive impact.
David Yarnold, president and chief executive of the National Audubon Society, a conservation charity based in New York, branded the findings “a full-blown crisis.”

What is the cause?
The study did not look into the causes as such, but researchers pinpoint habitat loss as a key issue, along with development, as mankind adds so much more infrastructure to the landscape, from buildings to windfarms. Pesticides are also touted as a factor.

What is the situation in the UK?
Although this study focused on the US and Canada, the findings are in line with declining populations around the world. 
The RSPB say that there has been “a serious, countrywide decline in the numbers of many birds, including many well known and loved species such as the song thrush, skylark, lapwing and house sparrow.”
The decline in the UK has been “gradual”, they add, saying that “extensive research has shown that these declines are caused primarily by changes in agriculture.”
And new findings from the British Trust for Ornithology say warmer weather is impacting the cuckoo, as well as the Little Owl and Reed Warbler.

What now?
Bird protection groups suggest individuals take action, from making glass more visible (to stop birds flying into windows) and keeping cats inside; while, on a grander scale, they call for greater conservation of bird-rich habitats.