Average number of individual birds and species, 2010-2016

Bird Nerd part 15: 2015-2016 data – catastrophe

If you have followed this blog for a while, you’ll know that I keep records of the birds I see in my garden. I have finally got round to entering and analysing the data from June 2015 to May 2016. The results make gloomy reading.

I have data from 36 observation days, spread across the year. On average, I saw eight individual birds from 4.5 species per day. This is the lowest average number of birds and species in the six years I have been collecting data, by quite some way. It’s a fall by more than half on the previous year’s average number of birds.

Average number of individual birds and species, 2010-2016
Average number of individual birds and species, 2010-2016

This averages hide a range from no birds at all (one day in February) to 19 birds from 9 species in June. In total, I saw birds from 16 different species.

As the graph shows, I started off with high numbers, which declined steeply in the first couple of months (as is fairly usual for the time of year). But the numbers never really picked up again, and December, which is usually the busiest month, saw very few birds visiting the garden.

Total number of individual birds and species, 2016
Total number of individual birds and species, 2016

How did different species get on?

The most regular visitor to the garden was woodpigeon, being recorded on 81% of observation days, followed by the reliable robin, on 78% of observation days. House sparrows were on seen on 36% of observation days, but turned up in numbers, giving a mean average of 1.8 individuals per observation day.

As the next chart shows, it was a bad year for most of the common species. The house sparrow population seems to have dropped dramatically from last year. I saw fewer starlings, collared doves and blackbirds than any previous year. Numbers of woodpigeons, magpies, dunnocks and jackdaws also seemed to be down on the previous year. Two species had their best ever year in our garden: robins and feral pigeons.

Average number of birds from common species, 2010-2016
Average number of birds from common species, 2010-2016

How does this fit with the national picture?

According to the British Trust for Ornithology’s Garden Birdwatch survey (which my data feeds into), There were low average numbers during the second half 2015. But they report that many of the seed-eating and insectivorous species were seen in very high numbers toward the end of the year,  something my data doesn’t reflect. There were low winter migrant numbers, which could have been driven by relatively mild winter.

Looking at the individual species, the latter half of 2015 does seem to have been bad for house sparrows, collared doves, blackbirds and starlings nationally.

What caused this decline?

I don’t really know what caused the decline. I haven’t changed the food, water or shelter features in the garden for birds. A couple of possible factors spring to mind.

  1. Last winter was very mild, so maybe birds didn’t need to visit the garden so much for food
  2. Cats and kittens: our garden is now used by next door’s cat – he probably arrived during this period. And our backdoor neighbours have got a couple of naughty kittens. So perhaps these are scaring the birds away.

And of course there’s the bigger picture that’s affecting birds nationally: Jazz, Roja and Kiki are not responsible for low numbers of birds nationally. Climate change, habitat loss and farming intensification are part of the longer-term story.

What to do?

I can’t change the weather, so I guess if I want to see more birds, I may need to discourage the neighbourhood cats. I am not sure how best to achieve this, without making the garden unappealing to Fat Cat as well, which would be a shame (she’s not a hunter – she once got scared out of the garden by a baby bluetit). Maybe we could use some kind of cat repelling sound device that we could turn off when Fat Cat is taking her constitutional stroll.

What do you think?

  • Have you noticed any decline in the number of birds visiting your garden?
  • Do you have any alternative hypotheses for why the birds have disappeared?
  • Do you have any suggestions on how I can discourage the neighbours’ cats while not spoiling Fat Cat’s chance for fresh air and grass?
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