Suddenly, the brown vegetation of winter gives way to fresh life and colour.

The grass has sprung into action – coating our dusty fields in a cool green cloak. Orchids glow between the tussocks like purple jewels, and Thrift blooms in delicate clumps among the rocks.

Thrift in bloom close to Flat Rock – last night, an Otter crept up behind us as we watched the sunset there!

The slopes around our shore have a diffuse mauve coating. Though they have been slow to open this year, the sweet fragrance of Bluebells mingles pleasantly with the salty air. Wood anemones and Wood sorrel glitter like a carpet of stars under the trees, and tiny birds forage in the branches for insects to feed their young.

The first Bluebell of the year… it doesn’t look too perky in this picture, but they soon livened up!

Many summer migrants are back to breed: Whitethroat, Blackcap, Willow and Garden warblers drench the shady paths in song. Cuckoos in the Pheasent Wood provide a soothing bass, but are best seen in the fields near Lephin Cottage. Driving along the track yesterday, I saw at least four individuals either wobbling gamely on telephone wires, or watching intently from fence posts. Incredible to think that they’ve traveled all the way from Sub-Saharan Africa! Seeing these birds again reminded me just how intriguing they are…

One of my favourite migrants: the Spotted Flycatcher – photographed just opposite The Lodge. These charming birds flutter through the trees after insects.  

Cuckoos are sometimes villainized for their parasitic lifestyle, with many people accusing them of being “lazy” or “poor parents”. In fact, female cuckoos invest some considerable effort in securing good foster homes for their young.

Think about it: in order to judge at what time she must deposit her egg into a nest, the female cuckoo must watch her targets carefully. Birds have a set incubation period (usually about 12 – 14 days for a small species). If the cuckoo mistimes her approach, she risks the host chicks hatching before her own, and damaging or destroying her egg.

One of the Swallows nesting in the Castle – very difficult to photograph in flight?! 

In some instances female cuckoos are known to eat clutches that are too close to hatching, in order to force the host parents to start laying again so that she can add her egg in. Her strategy relies on her egg hatching first, so that the cuckoo chick can eject the host eggs and be the sole occupant of the nest. This all sounds horrible, but when you consider that a female cuckoo can parasitise up to 50 nests a year… she certainly has her work cut out keeping track of them all!

A female cuckoo will only parasitise nests belonging to the same species as her own foster parents. This seems to ensure that her egg looks similar the eggs of her prospective foster family. If her egg looks dissimilar to other eggs in the nest (for example, if the colour pattern is different) it will be rejected and destroyed.

Her plumage helps to temporarily scare away the adult birds as she approaches; even I have mistaken Cuckoos for Sparrowhawks on occasion! Her blue-grey back, long tail and barred chest have evolved because of the benefits they confer. It takes her around 10 seconds to remove one host egg and replace it with her own – a remarkably quick process. Interestingly, if another cuckoo has already parasitised the nest, she seems unable to differentiate between the host eggs and other interlopers.

One of Glengorm’s Irish [mountain] hares in its summer pelt. Note that they are smaller than Brown hares. 

Once the cuckoo chick hatches, it assumes a murderous squatting stance. Using a special cupped area on its naked back, it shoves the other unhatched eggs over the side of the nest with gritty determination. This done, it plops cheerfully back into the middle and looks forward to being the sole recipient of all food brought by the adults.

You might think that the cuckoo chick would struggle here, as they are often much bigger than the natural chicks of their hosts. How could a cuckoo possibly grow on the slim-line diet of a tiny Dunnock?

Well, with an enormous brightly coloured gape (the inside of the mouth – seen when chicks beg) and a plaintive call that mimics a whole nest-full of hungry babies, the foster parents are driven to provide enormous quantities of food. Though able to spot foreign eggs on occasion, the adult birds have no mechanism for identifying foreign chicks. So long as the cuckoo keeps begging, the caterpillars keep coming…

Cuckoos of various kinds are known to target approximately 100 species of bird worldwide – in Britain these are usually species like Dunnock, Meadow pipit and Reed warbler.  The genetic processes linked to the colour of each bird’s eggs are still unclear. Originally thought to be determined by the female genes alone, it is interesting that in over 90% of studied cases, the chosen host also turns out to be the same species that fostered the male cuckoo.

Sadly, cuckoos are declining badly. Whatever you might think of their morals, their trademark song is surely one of Britain’s most evocative sounds. The British trust for Ornithology – BTO – began a program of tracking cuckoo migration in 2011 to try and discover why mortality is so high. For information about the results so far, see:

http://www.bto.org/science/migration/tracking-studies/cuckoo-tracking/what-have-we-learnt

Stephanie Cope

Glengorm Wildlife Steward