March Young Naturalists… on the search for elusive mice

What a weekend to run a Young Nats session! The weather was beautifully sunny and warm, a contrast to winter and a stark contrast to the cold snap we are having right now.

8 Young Nats arrived promptly at 10am, ready for the challenge of finding harvest mouse nests. Bob had kindly put the moth trap on the night before, so the Young Nats and Nigel set about checking the trap and identifying all the moths – I still have a lot to learn. I was very impressed with our Young Nats moth knowledge, and their eagerness to scrutinise the moth book when we found some we didn’t know straight away. We got a total of 11 species, including the Oak Beauty, and Hebrew Character.

Puzzling over moth ID

Having prepped some small mammal traps on Friday for Bob, the first thing I did after opening up in the morning was sneak around to see how many doors were closed.. quite a few! Once we were finished with moths we spoke about small mammal trapping and why you might do it (species diversity, species abundance if you were going to set out a grid and conduct a mark-recapture survey) and the requirements to ensure the animals’ welfare is catered to. These traps were set out close to the Education Centre, targeting voles and woodmouse/yellow necked mouse. We had more than half of the traps closed… but not all had occupants!

Some of our mice… especially our yellow necked mice have become rather crafty. They like to inhabit the loft in the winter, and become exceptionally adept at getting over the tripwire, eating the food, and out again. There were 5 traps during Young Nats that had tell-tale signs of mouse-habitation but open doors – I think the yellow necked mice we have released are playing tricks on us once more.

My focus for this trapping session was to have each Young Nat learn how to check a trap in a handling bag, and then to scruff the mouse/vole safely. The method is as follows – empty trap into bag, then remove trap and all bedding. Handling bags are large plastic bags with a seam along the bottom and two very useful corners. To keep the creature still you must wait until it is in a corner, and then bring a hand underneath the outside of the bag and around the animal to hold it snugly and firmly with its nose pointed into the corner. Then your other hand can enter the bag, and using thumb and forefinger you feel for the ‘scruff’ of the neck, focusing on feeling the shoulders and base of the back of the skull. Once you can feel these you take a pinch of skin and (if it’s enough skin and you’ve got an even amount from both sides) the animal will stay nice and still. This technique is used when surveying to sex the animal, place it in a bag for weighing, and to perform tasks like fur clipping safely if it’s a requirement of a survey.

I am very pleased to say that everybody managed to scruff a mouse or vole successfully, it does take a few tries to get it, and even though we had some apprehensive hands to start with everyone did well.

Fantastic scruffing of a woodmouse

After lunch we headed out to the north of the reserve, sticks and tape measures in hand to do a final search for harvest mice (winter surveying finished 31st March). I will do a separate blog about our winter harvest mouse surveys, to give final numbers etc soon.

In an attempt at a brief summary – we measured out two 10 x 20m squares to survey, in an area between Goosander and Lapwing Hides that isn’t accessible by the public. What does access it lots however.. is the deer. Frustrating though their numbers can be, they have made useful tracks so that we could navigate our way in and set up the survey.

Harvest mice build their nests around 30cm up in the grass, woven into little tennis ball sized spheres. They strip the grass into pieces and weave it while it is still attached, which means their nests stay suspended long after they leave. We were searching for 2021 breeding nests, which thankfully still persist in the grasses… but as the grass had been flattened by deer and wind we had to be very thorough.

Using gloves and sticks to help separate the grasses, we all begin a focused search for nests. Nigel, Geoff and I were assisting, and after about 15 minutes there was a yell of ‘I FOUND ONE’ from one of the girls, and excitement from the rest of that team. Once we knew they really were there, and we COULD find them… the focus turned into a forensic type search with some very careful searching and in total we found 4 nests. Absolutely brilliant work from everybody involved, and this adds to our previous finds from this winter’s surveying which is our first ever evidence of harvest mice in the northern part of the reserve. Well done Young Nats, and our volunteer surveyors this winter!

On the hunt for harvest mouse nests

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The Blues

The last few days have seen warm sunshine by day but chilly nights, meaning it has been poor for moths but good for day-flying insects. Today at Blashford Lakes I saw my first scarce chaser and downy emerald of the year and there were other dragonflies about too with reports of emperor, broad-bodied chaser and hairy dragonfly.

Most of the butterflies that over winter by hibernation as adults are getting scarce now and spring species such as orange-tip are dropping in numbers. there are a few whites around with all three of the common species, but the highlight today was the emergence of  blues. The small meadow near Ivy North hide had six or more male common blue as I went to lock up and at least three brown argus as well, the argus is brown, but an honorary “blue” all the same..

common blue (male), freshly emerged.

The brown argus look very like small female common blue, and the male common blues will get up to chase one if it flies by, however they quickly realise their mistake and give up. The first emergences are all males and the females will follow in a day or so. The reason for this is the same as that for male migrant bird arriving just ahead of the females. Evolution will push the males to be in place and ready for the first females to arrive, it does not pay to be late, so the pressure for males to be early is greater than that on females, who can afford to wait until they know there will be males to mate with.

The spring solitary bees are starting to disappear now, many species collect pollen from just a few plants and as these cease to flower they need to wrap up their breeding cycle. I did come across one interesting species today though, it was one of the nomad bees and the smallest species of them to be found in Britain, Nomada sheppardana.

Nomada sheppardana on forget-me-not

Visiting flowers is something many insects have to do to feed, it may sound an unproblematic things to do, the flowers want to offer a nectar reward, or perhaps bribe might be a better description, to the insects that will pollinate them. However it is not as safe as it might sound, flowers can hide predators, especially the camouflaged crab spider which match their colour to the flowers they sit on.

crab spider with hoverfly prey

The crab spider here matched the hawthorn flowers so well that I missed it and initially set up to take a picture of the hoverfly, only then did I see the spider!

It has not been a good year for ground-nesting birds so far this spring, with most lapwing and little ringed plover losing their eggs to predators. I suspect mammals at night as the ones nesting on the islands are doing much better. Or at least they were, on Thursday might all the black-headed gull on Long Spit abandoned their nests. Although I don’t know for sure I suspect that something swam out there and ate their eggs, probably a fox or a badger. These mammals are usually not that keen on swimming, but if they are hungry they will go to great lengths to get the food they want, I think small mammals, which are their preferred prey, are in short supply this year, which might be why they are seeking birds eggs more actively.

Despite a bad time for some ground-nesters the pair of oystercatcher are still doing well, with their two chicks growing well. They hatched on Long Spit, moved off to the shore near Tern hide and have now returned to Long Spit, this meant they were not out there on the night of the predator raid. So far the main gull colony on Gull Island shows no sign of being attacked and neither do the tern rafts on Ivy Lake.