26/03/15 - Changing of the seasons

The last two weeks have been full of the signs of spring and the changing of the seasons, at the beginning of the month whilst working in the office one morning, in carried one of our favourite sounds - the trumpeting and bugling of Whooper Swans - arriving from the south. We managed to spot one herd of 89 as they dropped down onto Wheldrake Ings, but from the sound we thought more may have already arrived on site. A quick trip down there revealed that there had been a major arrival, with a staggering 362 present on the floodwater – this is the largest herd ever recorded on the Ings and represents around 3% of all the wintering Whooper Swans in the UK.

Although the birds were on the water (meaning we unfortunately couldn’t read any potential colour-rings to see where they had come), we can however suggest what these birds were doing thanks to two satellite tagged birds that arrived in a similar way a few years ago, and the behaviour of spring herds in recent years. It appears that birds that have been wintering on the Ouse Washes in Cambridgeshire (including WWT Welney) depart there just after dawn. These birds then arrive here in the Lower Derwent Valley around 2-3 hours later, and spend the day in the valley, loafing, preening, drinking and resting up before they depart shortly prior to dusk. In the case of the two satellite tagged birds they were then logged heading over Loch Lomond north of Glasgow at around 11 pm before heading out over the sea from the Scottish mainland at around 1am, arriving in Iceland some 12 hours later – that’s a nonstop flight of 18 hours after departing the LDV. It also means that the valley is an important spring migration stop-over site in which to re-fuel and rest before their long journey to Iceland. We wish these magnificent birds well on their journey which could see them fly as high as 27,000 feet and in temperatures down to -40 degrees and look forward to their return in the autumn.

Whooper Swans - Wheldrake Ings - 11/03

Grey Herons have been seen frequenting the local heronry lately and soon it’ll be time to start having a look around the heronry for signs of activity, last year we visited the heronry on the 31^st March and found a number of egg shells beneath the trees. Herons are one of the earlier nesters, with some records being as early as February for birds on eggs. Herons have bred in the heronry here for at least 40 years, along with Little Egrets in 2010, which went on to produce two young. Herons are rather sociable birds, breeding in close quarters and are known for nesting in long established heronries, with data going back as far as 1928 when the first survey by the BTO took place. Last year thirty young herons were ringed on just two visits, with six re-sightings being had since then.

 Grey Heron - North Duffield Carrs - 04/03

The recent warm days have brought out the first reptiles of the year with both Common Lizards and Grass Snakes seen during the second week of the month. Despite the recent cold starts, by mid-morning the sun has been giving off enough heat to lure some of our reptiles out into the open, with a Grass Snake showing regularly around the bomb bay loop, basking in little pockets of sunshine. After a winter spent in hibernation, Grass Snakes start to venture out into the open during March/April as the weather warms up. At this time of year they need to spend time basking to warm up their body, early morning is the best time to look for them, before they warm up enough and disappear back into the cover of vegetation. After spending the first few days around the hibernaculum they will then start to move away in search of food and a mate.

 

 Grass Snake - Skipwith Common - 11/03

Barn Owls are still treating the staff, volunteers and visitors to long and prolonged views, with several individuals hunting almost daily from morning - afternoon at Bank Island, Wheldrake and North Duffield Carrs in particular. Last week we were spoiled with unbelievably close views of this individual which we observed hunting for long periods of time. It was present in the field adjacent to the office, from as early as 9 o’clock in the morning until dusk.

 

Whilst sightings of Barn Owls hunting in the day time are common at the moment, it seems to have brought about the question as to why….. Owls usually only hunt during daylight hours during the summer months when they are feeding hungry broods, meaning they have to hunt for longer to supply the demand for food at a time when darkness covers less hours. They are also forced to hunt during daylight when wet or prolonged cold weather reduces feeding opportunities. Given that this winter has been mild and relatively dry, we are left wondering if perhaps the vole cycle might be at a low ebb and the owls, although hunting regularly, just aren't finding enough food. Five birds have been picked up dead around Bank Island and Wheldrake Ings over the last few weeks – which leaves us wondering if these birds are starving… One of the fresh birds we picked up last week only weighed 200g which would suggest this to be a possibility. Perhaps our recent small mammal trapping might shed a bit of light on the vole population at Bank Island and help to answer a few questions.

It might also be worth mentioning that Barn Owls mainly hunt by sound, and in most parts of the world they are nocturnal because their prey is nocturnal. In the UK there is evidence to show that diurnal hunting has become more frequent over the last 100 years. It is thought that this could be a shift in diet from mice and rats which are nocturnal, to Field Voles, which are more active during the day. Whatever the reason, the daytime hunting birds are certainly proving a popular attraction to local and visiting photographers, this individual was snapped by Dan Lombard whilst volunteering with us for the day.

 Barn Owl - Bank Island - 11/03

Roe Deer are a regular and daily sighting at the moment in the valley, with groups of seven seen at Wheldrake Ings and six at Bank Island. Although Roe Deer are often solitary for much of the year, they do form small groups over the winter – often comprising of several adult females (does), yearlings and a single male (buck). The males start to grow their antlers over the winter, and by the spring they are covered in soft velvet. Over the coming months the males will start to shed their velvet by rubbing their antlers against trees or branches in time for the autumn rut.

Having mated following last year’s autumn rut, the females will be giving birth soon in the meadows during May and June. People often find these fawns and think they have been abandoned, however the females will be watching from a distance and will return so please don’t be tempted to approach or move them!

 

Roe Deer - Wheldrake Ings