Dalkey Tidy
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Wildlife Newsletter for the Township of Dalkey
April 2007 - Michael Ryan

Nest Boxes for Birds
A lot of birds will have built a nest by now due to the mild spring but not all and sometimes birds that nest early can lose their early clutch through sudden drops in temperature or disturbance. Birds that nest in dense bushes are not to know somebody is going to be coming along soon with hedge clippers or mechanical trimmer to cut it back, leaving their newly constructed home destroyed or exposed. If birds are nesting in your garden they are going to make sure you do not see them going into the nest so it is recommended that the best way of checking hedge or bush is to get down low and look up to see the mass of twigs silhouetted against the light.

If you have a nest box at least you will know where the birds are. It is very enjoyable watching the adults come and go never failing to wonder at the work the parents put in constantly feeding their young, making hundreds of visits during a single day. A big industry has developed in Europe and the US making nest boxes with built in video cameras which connect to a monitor or to your television so you can watch what is happening inside the nest box, the eggs being laid then hatched, the chicks growing and being fed and eventually taking their first flight. Nest boxes can also serve a useful function outside the nesting season as birds use them as a safe, warm roosting space in winter when a number of birds may cram in to a box together. Apparently somebody has recorded over thirty wrens piling into a Blue Tit nest box together. Many years ago I bought a House Martin nest box, a little plastic dome nicely finished to resemble the moulded mud of a real nest. I fitted it under the eaves of the house outside the kitchen where it would be out of direct sunshine. To the best of my knowledge no House Martin ever even looked at it, let alone tried to nest in it but it did serve a function. One evening in mid summer I saw a adult wren clinging on to the pebble dash wall a few inches below the nest box urgently calling. Suddenly young wrens started appearing out of the bushes and the adult bird seemed to be ushering them into the nest box. It was a complete reversal of the usual procedure when adult birds urge fledglings to leave the nest to which they rarely return but it was probably due to a peculiar aspect of wrens breeding habits. Sometimes before a brood of wren chicks are fully reared the female will start brooding and hatching another clutch leaving the male to look after the previous family and I imagine this was what was happening, the male adult wren taking the first family to safety in the nest box. I have seen the wrens nesting in it subsequently and suspected one might be roosting in it in winter. One night in late winter I slammed the lid of a bin and saw a wren darting out of the box closely followed by another and another, then one more, then two more. Six birds came out before I went back indoors afraid of keeping them out of their warm refuge so there may have been even more squeezed in there. Fiercely territorial during the breeding season they can all cram in together when the need arises.

Buds on Ash and Oak trees will soon start to open containing the tightly packed leaves which have been storing up energy since last autumn. Apparently scientists are studying buds of hornbeam trees to develop practical applications from seeing how they can compress so much into a very small density. Usually the first buds I notice opening on a tree is on a particular Horse Chestnut on the Vico Road whose own micro climate brings them out early in March but this year there were leaves on elder bushes in January. Buds opening early due to a milder climate can spell trouble for wildlife since complex feeding chains have developed over millions of years with caterpillars feeding on the fresh young leaves then birds eating the caterpillars or in the case of Great Tits feeding then to their newly hatched chicks. If the leaves open too early they will be too tough to digest by the time the caterpillars emerge and subsequently they won’t thrive to feed the birds and their chicks.

Dalkey has a good range of native mammals including fox, badger, rabbit, red squirrel and possibly even stoats and it’s urban wildlife that will be the subject of a illustrated talk by conservationist Billy Flynn at the Kingston Hotel in Dun Laoghaire on Tuesday 3rd April