Around 70,000 animal lovers dusted off their binoculars and set themselves up in gardens and parks across Germany to take a look at the birds swooping around their neighborhoods. Over a period of an hour, spotters noted the types and numbers of birds they saw - their descriptions detailed in the fifth installment of a series of surveys conducted by the Nature and Biodiversity Conservation Union (NABU).
Citizen science meets bird spotting
To make it easier for participants, who were not required to be experts on the different species, NABU provided detailed instructions online. Whether they saw a blackbird, a brambling, a great tits or another type of bird entirely, volunteers were asked to identify them from a list of photos and check a box - a demonstration of citizen science at its best.
Online participants were able to access and follow the number of birds that had been seen, as well as view a ranking of the leading species.
The purpose of such surveys is for NABU to discover more about the development of Germany’s common garden birds - and it's a method that's working.
In January 2014, when the last winter bird survey was conducted, more than two million of these feathered friends were counted over a weekend. The house sparrow - known simply as a sparrow - was the most spotted. The great tit followed in second place, with the tree sparrow coming close behind. Around 76,000 volunteers took part in the count.
"This year, not much has changed in terms of numbers," said Eric Neuling of NABU in Berlin.
Around two million birds were counted by 70,000 volunteer spotters. He was, however, very satisfied - there has been no worrying decline among the birds.
The fact that tits were not seen as much was to be expected, Neuling said.
"When there is as mild a winter as this, fewer tits come from the north and east to Germany," he said.
And also, they were generally not seen so often in gardens if they could find sufficient food elsewhere. In that way the sparrow is more trusting.
But particularly striking this year were the findings with regard to the starling.
"A certain number of starlings do not migrate during the winter - that's normal," said Neuling. "This year, double the number of starlings were observed in Germany, compared with last year."
The impact of mild winters
Normally during winter, starlings would fly south to France or to the region south of the Alps. Only a few of the birds stay in southwest Germany.
That's "because it’s generally milder there than in Brandenburg or Mecklenburg-Vorpommern," said the NABU expert.
This year, however, experts were surprised to find some of the birds remained in the northern foothills of the Alps.
"You can clearly attribute this to the mild winter," said Neuling. Starlings usually shun the cold temperatures.
Other birds that also fled the cold temperatures of their home region were the waxwings. They are typical guests in Germany over the winter, coming from even colder regions such as northern Scandanavia. This year, however, a significant number of the birds did not fly as far south.
"This is because the food supply in their homes over the winter was more than sufficient. The birds did not consider it necessary to continue further south," explained Neuling.
The problem birds
Particular attention was paid to the greenfinch, which came in sixth place.
"Since the beginning of the counts, numbers have been steadily decreasing - now for the fifth time in a row," said Neuling.
The number today is around 40 percent lower than in previous years, and numbers have fallen even further this year.
"The single-cell parasite Trichomonas gallinae is to blame. It lurks particularly where the birds feed and get water," said Neuling.
Danger of infection was particularly large in places where many birds gather together. But other types of birds were not so susceptible to the bacteria, he explained.
But there are things that could be done to prevent infection.
"You have to make sure that the feeding area is as hygienic as possible," said Neuling.
There should be no areas where the seeds are spread around in the open for the birds to walk in. Instead, feeding silos or barred feeders should be used.
"These are good measures with which everyone can help to protect the greenfinches," added Neuling.
Whether that works will be seen next year.
The next bird count is already fixed: the first weekend of May - the weekend dedicated to garden birds.