In which we find woodmice, bank voles, field voles, and pygmy shrews but no harvest mice

As the alarm went off at 5.20am the other day, I did wonder why I had let myself in for such an early start on a precious day off. The rain beating against the windscreen as I drove through the dark, empty roads didn’t encourage me, either. I pulled up in the near deserted superstore car park, and it crossed my mind that this was not a normal thing to be doing.

The rain had stopped by the time I had got out of the car and wellified myself, and the remains of the supermoon cut cleanly through the sky. Our small group of like minded eccentrics congregated and headed off down an obscure path in the corner of the car park, lighting headtorches as we moved out of orange glare of the street lamps.

The path went under the dual carriageway, beside the river, to an isolated area of  waist-high marshy grasses, visible only in the small patches illuminated by head torch beams. After a bit of searching, we found the cached hoard of straw, food and weatherwriter, and stocked up the black bin bag. It didn’t look at all suspicious, four people walking around deserted wasteland at 6am in the morning carrying a black bin bag. I did wonder what anyone looking out of a window from the houses across the river must have thought.

We headed into the grass towards the scrap of striped tape that marked the first trap point, where two longworth traps (one on the ground, and the other set a couple of feet up on a stake) waited.

There’s always a frisson of suspense as you approach a small mammal trap. Has it been tripped? If so, what will it contain? We had a bumper harvest that morning – 8 woodmice, 2 field voles, 2 bank voles and one fiesty pygmy shrew. But none of the animals we were really searching for: harvest mice.

Field vole
Field vole

As the bright November morning dawned, we were able to get a better look at what we caught. If you think that one small mammal species is much like another in temperament, you’re mistaken. As you can see from these photos, voles are pretty chilled. I didn’t get any photos of woodmice (it was too dark when we found them, and they move too quickly). The tiny pigmy shrew was my personal favourite. You’ve got to admire a creature that, though about as big as a thumb nail, decides to try to bite its captor’s hand (it’s teeth weren’t long enough the penetrate the skin, but it gave it a good go).

Pygmy shrew trying to bite
Pygmy shrew trying to bite
Vole
Vole

The check was part of Surrey Mammal Group and Surrey Wildlife Trust’s harvest mouse project. We’re trying to get fur samples from harvest mice populations in different sites in the county. These samples are then DNA tested to allow us to see how closely related they are, or whether harvest mice at different sites have very different DNA to each other. The point of this is to see how good the connectivity between sites is for wildlife. Connectivity is important, as isolated populations are vulnerable to being wiped out.

This is our third year of the project. In the first year we were able to get enough samples for the lab scientists to identify plenty of DNA markers that will allow us to compare different harvest mice populations. Last year, when we went back to survey the sites that had had lots of harvest mice the previous year, we found very few. And we’ve not had large numbers this year, either.

We repeated the survey that evening, starting and ending in the dark, and found similar numbers of woodmice, bank voles, field voles and a single pygmy shrew, but again no harvest mice. The voles decided that sitting on hands was a morning activity – in the evening it’s all about climbing onto heads. This one seemed to particularly enjoy Derek’s hair – it looked like it was planning to settle down up there. Glen and Keith also got scaled by intrepid vole explorers.

A vole in the hair...
A vole in the hair…

By the end of the check it was bucketing down, and I was very pleased to get home to a warming bowlful of food, prepared by Dr C.

It’s not hugely surprising we didn’t find any harvest mice at this site – it really is cut off from other harvest mouse habitats (I suspect voles and woodmice are a little less particular in the sorts of neighbourhoods they’ll live in). And, while we didn’t succeed in our aim for the checks, it was still great to see small mammals at such close quarters. And it was worth braving the elements and giving up a lie-in to have that privilege.

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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?

Belated nest discovery 

The mild weather of October has given way to a chilly November. Time to get ready for winter. So Dr C got the ladder out to take the camera out of the birdbox, which is hidden behind a tangle of clematis by our front door.

This year was disappointing for birdbox activity. We had a pair of bluetits who started building a nest, but they abandoned it before laying eggs.

So it was a little galling when he discovered a birds nest on top of the nest box. It looks like birds did nest this year, on rather than in the bird box. And all this time, it was easily watchable from our sitting room, if only we had known to look.

Bird nest on top of the camera nest box
Bird nest on top of the camera nest box

I am not sure what sort of birds nested there – it looks quite different from the many bluetit and wren nests I have seen, but they have usually been in a box, rather than freestanding. Any ideas? My best guess would be robins, given how frequently I saw them in the back garden this spring.

I’ve no idea what happened in this nest. Was it abandoned before any eggs were laid, like the one in the box? Did they lay eggs? Did the chicks fledge. I will never know. I would like to think they did, and that perhaps they will be back next year. I will certainly be keeping an eye out for them!

Do you have any ideas about what made the nest?