Anticipation mounts for Osprey egg hatchings

May 29 2009 by Our Correspondent, Dumfries Standard Friday

THE EXCITMENT is building with the hatch date of the first of the three osprey eggs due this Sunday, May 31.

It is a bit like being an expectant father all over again! The great thing is that we can watch it all happen via the CCTV system that beams live pictures form a camera actually attached to the eyrie back to the centre.

The incubation has been going well despite the very wet and windy weather at the beginning of the month.

Both birds take their turn on the nest with the female doing the bulk of the sitting. However the male takes his duties seriously as we saw one day last week when she returned to the nest after feeding and had to physically pull him from the nest by grabbing his wing in her beak.

There will be a special Caerlaverock Osprey Day at the WWT Wetland Centre with free entry for all next Saturday, June 6 to celebrate the return of ospreys to Dumfriesshire and hopefully the chicks hatching.

There will be walks, talks, activities and experts on hand throughout the day from 10am to 5pm.

For the younger osprey watchers we will have osprey hat-making, and osprey fishing game and building a life-sized osprey nest.

Caerlaverock is alive with bird song at this time of year with large numbers of breeding birds all over the reserve.

A pair of little grebes are sitting on eggs on the teal pond. Our resident mute swans in the meadow should be ready to hatch any day now and there are now ten pairs of black-headed gulls sitting on islands in the flood ground along with one pair of oystercatchers.

Six other pairs of oystercatchers are looking good on the teal, whooper and folly ponds.

There are over twenty pairs of Lapwings fiercely defending territories on the reserve with five pairs of Redshank with a strongly held territory on the east merse.

The reserves heronry has 14 active nests in it and last year’s successful buzzards are back and sitting on eggs.

Our barn owls laid four eggs this year and one has hatched already and the second is due today.

As usual we can watch it all happen via our CCTV system.

There are also good numbers of breeding passerines across the reserve including stonechat, whinchat, reed bunting, skylark sedge and willow warblers.

Birds that have passed through this month include a wood sandpiper and three garganey that were all last seen on the folly pond onMay 9.

Another egg hatching event has brought a near extinct creature closer to safety.

The Tadpole Shrimp, Triops cancriformis was discovered in 2004 by Dr Larry Griffin of WWT in a temporary pool on the Caerlaverock NNR.

This was the first discovery of these rare crustaceans in Scotland for 40 years, they are found at only one other site in the UK.

These amazing creatures are described as a living fossil and are unchanged from those found in the fossil records from 300 million years ago.

The eggs can lie dormant in the mud for decades until conditions are right for them to emerge.

They appeared again in the same pool in September 2008 and we took four adult hermaphrodite females from the wild population under licence from SNH once we knew there was a good number of adults in that colony.

These females were then kept in a three foot fish tank, where they were given a muddy substrate to forage and grub around in and fish food and cooked carrot every other day.

After a few weeks they were observed digging egg pits into the substrate and then burying these pits.

They shed their carapaces or skins at least four times each before eventually dying on Christmas Day.

Their egg loads are renewed each time they shed their skins and it was thought we would have got about 400 eggs from each of these adults during their three months in captivity.

The tank was then dried down over a few weeks and the mud divided up into portions in which it was hoped there would be 100 or so eggs. The mud samples were then bagged and one was put in the freezer for a few days, it was then removed, placed in a small tank and wetted up again at about 20 degrees.

After 48 hours the tiny nymphs could already be seen swimming about the tank with the orange hatched eggs floating on the surface (1mm in diameter).

The idea is to maintain the genetic integrity of this population within these stored samples so that they could be rejuvenated should the single current population in Scotland go extinct e.g. through inundation and erosion by the sea (the single pool being on the Caerlaverock NNR joint managed by WWT and SNH) as happened back in the 1960s at Southwick/Preston Merse area further west on the Solway where the species used to be found.

The species is currently only found at one other site in the UK at Godshill Pond in the New Forest, thus preserved genetic material that can provide hatchlings at a later date (and it only takes one hermaphrodite hatchling to provide what is needed for a new colony) may be useful for any Species Recovery Plan which might be envisaged under the Species Action Plan currently being reviewed, whereby sites that used to hold populations could possibly be repopulated should suitable habitat be identified.

In theory the unhatched eggs in the mud samples should remain viable on the shelf for anything from two to three decades and as such will remain an extremely effective ex situ conservation tool for the preservation of this species, much as a seed bank does for plants. We hope to exhibit the adults in a tank at the centre this summer.

Next Sunday, June 7 is the first of our Merse Walks. These special guided walks will take you to places never before visited on the vast saltmarshes of our reserve.

The emotive sound of skylarks singing from the sky above, the carpet of pink thrift, meadow pippits flitting from fence post to fence post and the Lochar Water meandering gently to the Solway.

The walk starts at 2pm and is about 4 miles long over uneven ground, stout footwear and binoculars are recommended. Normal admission prices apply to all, to book a place phone 01387 770200.