Gizzard stones

Another surprise.  I found an old pellet on the roof, trapped in a hydrangea branch that had grown over the tiles.  I assumed it had been regurgitated by a tawny owl sitting on a branch of the oak tree above.  The pellet was hard and about 40mm by 10mm.

I could see a claw and what looked like a small stone and a piece of insect wing case but not much else.

A tawny owl pellet is mostly made of fur and will break apart easily to reveal the bones inside - usually the bones and skulls of three or four small mammals.  This one was tough so I soaked it in water.  It was still difficult to tease apart because it was made of decomposed feathers rather than fur.  And the largest bones it contained were the legs and feet of a bird.

So now I think the pellet is not from a tawny owl at all.  The bones were all broken - an owl swallows its prey whole. There were quite a few other bone fragments but no skull or other parts that I could recognise.  My best guess is that the pellet is from a sparrowhawk.  I am a bit puzzled by what look like a few strands of grass, best seen in the top photos.  They were much less obvious in the grey mush once the pellet had been teased apart in water.  I can understand how a bit of grass might be swallowed during eating but I would have expected it to be digested easily. Here are the pellet contents, minus the feathers.  You can see the claws, two lines of bone fragments, skin strips, stones and a few small bits of insect wing case as well.

The several small torn fragments of skin look like bird skin.

The most intriguing finding was these four small stones, about 5-10mm in diameter.

Birds can't chew and they mash up their food in a muscular stomach, the gizzard.  Many birds swallow small stones to help this process, stones known as gizzard stones or gastroliths.

Plant-eating dinosaurs used gastroliths as well.  Their stones were much larger and stayed inside for years, becoming smooth and rounded like pebbles on a beach.  I found this photo of Jurassic gastroliths on Wikipedia.

Pop goes the weasel

Ever since the weasel turned up in the garden in the summer I have been trying to get another picture.  Inspired by the Mostela*, a trail camera box used for monitoring stoat and weasel populations, I built one similar from a translucent plastic storage box (£7 from Dunelm).  There are two holes at one end and a trail camera at the other.  The Mostela was designed by Jeroen Mos, an ecologist and small mustelid researcher in The Netherlands, and is an enclosed box with a cutaway plastic pipe connecting the two entrance holes.  Wanting better pictures in a more natural setting, I made mine to admit natural light and built a small "stage set" of bark and loose bark chippings at one end.  The trail camera has a +2 dioptre lens to cope with the close focus.  It can record in colour in daylight but reverts to infrared when the light is poor or at night and it is then augmented by a motion-activated battery-powered infrared security light (a Brlnno APL200).  This is a view of the box with the lid removed.

Here are the camera and the infrared light.

This is the "stage set".

Here is the box in the garden with two Victorian land drain pipes as access tunnels.

Like other small mustelids, weasels are very inquisitive animals and will investigate any small hole which might contain prey.  For the first few days I baited the camera box with sunflower seeds so that it would smell of voles and mice but recently it has been left as it is (although mice and voles still visit every day).  I had the camera box set in my garden and the local nature reserve for four weeks before a weasel eventually made a brief appearance this week.  In fact it was very brief so I have added a 25% slow motion replay to the video.

Several other animals are much more regular visitors.  They include wood mice, always at night and so in black and white.  Wood mice visit every night and spend a lot of time in the box.  There is no food for them but perhaps it is warm and dry and feels safe.

Bank voles more often appear in daylight.  It is a pity the weasel didn't stay this long.

Common shrews also mostly turn up in daylight.  This clip also has a 25% speed replay.

Pygmy shrews appear both in daytime and after dark.

And a couple of very unexpected visitors.  Both birds were in the box for over two minutes and got rather agitated when they couldn't find the way out.

I plan to leave my weasel box set in the hope of more recordings and, perhaps, one day even a visit from a stoat.

* Mos J, Hofmeester TG.  The Mostela: an adjusted camera trapping device as a promising non-invasive tool to study and monitor small mustelids.  Mamm Res. 65, 843-853 (2020). https://doi.org/10.1007/s13364-020-00513-y

Even more moths

Since my last post on moths in the garden I have been setting the trap every week or two and each time I find moths I haven't seen before - apart from the latest time when the only thing in the trap was a crane fly.  The species count is now over 100 although there are also several mid-sized greyish-brown jobs I am not sure about.  The rest of them have been spectacular so here are few of the recent beauties I can identify fairly confidently.

Blood-vein,

Canary-shouldered Thorn,

and Centre-barred Sallow.

I joined the North East Garden Moth Scheme meeting in Gosforth Nature Reserve one evening and saw these three - Herald,

Devon Carpet, apparently a first record for the county,

and Small Phoenix.

Back in my garden - Pebble Hook-tip,

Silver Y,

Mother of Pearl (a micro-moth, but rather a large one),

Copper Underwing,

Dusky Thorn,

Shuffle-shaped Dart,

Angle Shades,

Rosy Rustic,

and Red-green Carpet.

The last is the second largest moth I have seen - a Red Underwing.

That's it until next year.  I look forward to next spring to see what will turn up then.

Ladybird, ladybird, fly away home

The weather here has been odd in October, down to 1℃ on one night recently but up to 20℃ on a few days.  One one warm day last week there was a cloud of ladybirds on the south-facing wall of the warden's lodge at the nature reserve. They were all harlequin ladybirds (Harmonia axyridis) and my friend Phil J counted them - 670 - although I think he may have missed one!  We saw several different colour forms.

When I got home I found about 50 on the wall of my house.

Then this week I found them on the ivy in the copse at the north end of the garden.

Alongside the adults I found several fifth stage instars (larvae),

and pupae.

One of the reasons Harmonia axyridis is so successful is that it can breed so late in the season.  The larvae have to pupate and the pupae emerge as adults before hibernating this winter.  Breeding is long since finished for the native species.

Harmonia axyridis is a non-native invasive species that was introduced from Asia to Europe to control aphids and has since spread to the UK.  It arrived in 2003 and spread rapidly across the country, reaching the North East in 2010.  It and its larvae eat aphids but will eat all sorts of other insect larvae as well, including those of our native ladybirds. Large aggregations form on warm days at this time of year, looking for a place to hibernate.  

Harlequin ladybirds come in many colour forms, even though they are all the same species.  The three commonest forms are f. succinea, yellow, orange or red with 0-21 black spots,

f. spectablilis, black with four orange or red markings,

and f. conspicua, black with two orange or red markings.

Here are some of the other variants in an image from Wikipedia © entomart.

Ladybird, ladybird, fly away home

Your house is on fire, your children are gone,

All except one and her name is Ann,

And she hid under the frying pan.

The meaning of this nursery rhyme is unknown.  For discussion of the possibilities see Wikipedia.