January 2017

Fieldfare (In this case in Northern Europe in Sweden)

The holly and the ivy when they are both full grown – provide many species with food and shelter.  Well I think I got the first part of the carol right.  At this time of year as the weather and the countryside become increasingly grey, evergreens like holly and ivy leave a welcome splash of colour.  This is particularly true of holly with its bright red berries.  The berries provide an obvious food source for wildlife and in January song-thrushes and blackbirds will gorge themselves on them at a time when other food sources are scarce.  There may well be an influx of their less well known cousins the fieldfares and redwings from northern Europe also taking advantage of the berries.  Ivy berries, though less conspicuous than holly (They are a rather attractive velvety black colour and smaller than holly berries) also provide a welcome energy source for many birds.  Ivy flowers quite late in the season and the small easily overlooked flower clusters provide nectar and pollen for many insects, not least the ivy bee* (Colletes hedera) which emerges late in the autumn to take advantage of these flowers.

Ivy Flower - 

In terms of providing shelter, ivy provides plenty of nesting sites for birds like the robin, dunnock and wren.  It provides a good tangle of stems with plenty of leaf cover and is usually growing over a good solid wall or fence that offers a bit of insulation and protection from the wind.  The holly too provides nesting sites for many birds.  The prickly leaves make it very difficult for ground-based predators to climb into.  I recommend that you don’t clear up dead holly leaves from beneath the tree as cats won’t go anywhere near it.  The fact that holly and ivy don’t lose their leaves in winter means that birds can build nests in early spring that would be otherwise exposed in a deciduous tree before its leaves have sprouted.

 Of course, there are animals other than birds that feed and take shelter in holly and ivy, not least of which is the holly leaf miner.  This is a species of fly that lays its eggs in the leaf.  When the eggs hatch the larva (maggot) eats the inside of the leaf between the tough outer layers.  This eventually pupates and emerges from the leaf as an adult fly – if all goes well, that is.  There are a couple of species of parasitic wasp that lay their eggs inside the larva which hatch and eat the larva from the inside.  It’s gruesome but the holly has indirectly provided food and shelter for yet more species.  And it doesn’t end there because birds like blue tits and great tits can get at the larvae before they emerge, to add yet more species to the list provided for by the tree.  Even though the holly bears the crown, the ivy isn’t left out as regards leaf miners.  The ivy leaf miner is a micro-moth larva which starts eating inside the leaf but when it is big enough to moult, it leaves the leaf and spins a cocoon outside.  The micro-moth is the small grey tortrix (Cnephasia incertana) which is a common species that we often find in the moth trap.  (It isn’t restricted to ivy; it mines several other plant species.)   The holly and the ivy each support only one species of leaf miner which, considering the large number of leaf miners, makes them quite a selective host.

Though the bark of most trees carries mosses and lichens, I don’t remember seeing lichens on the smooth bark of holly – hmmm,  more research required.

* The ivy bee was described as new to science as late as 1993 from specimens found in southern Europe.  It was first found in the UK in 2001.