BIRDS AS AN INDICATOR OF ENVIRONMENTAL QUALITY

About 12-15 years ago, agriculture began facing up to the adverse impacts it was having on the environment. With assistance from Europe, many schemes were introduced to reduce environmental impacts, most notably the Rural Environment Protection Scheme. But farming still has a long way to go to avoid further extinctions in Ireland's native plants and animals.

The other major force in the rural landscape, forestry, is only now beginning to acknowledge that it can also severely impact on natural habitats and native biodiversity - though it has been dealing with its visual impact on the scenery for some time.

The Forest Service has invited comments on its review of forestry legislation; Coillte has issued a short document on sustainable forest management; The national strategy on forestry aims for at least 10% of new plantings to be broadleaved trees; a national millennium forest project will focus on the semi-natural broadleaved resource.

The ranks of foresters are thus lined up on the bank of the Rubicon, about to cross - though many people say they will need a push to get into the water.

The indomitable Tony Lowes has convened a Coalition for Sustainable Forestry, backed by all the major conservation NGOs, to provide that push, and it looks as if forestry may be entering a new era.

Certainly, there is a new awareness and appreciation of broadleaved trees and woodlands, thanks in part to the campaign by Jan Alexander, who founded the group Crann in 1986.

This has resulted in a slight increase in commercial broadleaved plantings. It has also encouraged individuals and communities to plant trees, groves and small broadleaved plantations for aesthetic and amenity purposes, to improve the landscape and the air, and to do their bit for the conservation of native birds and animals, because, as we are continually reminded, broadleaved woodlands can be the most species-rich natural habitat in Ireland.

Once you've established a new broadleaved plantation, or started rehabilitating an old one, the next logical step is to look at how your woodland management methods are affecting and benefiting wildlife.

If sustainable forest management is the goal, then we need to look at these things, but it should be emphasised that it is quite possible to combine commercial timber production with conservation of fauna and flora in broadleaved plantations - the models for this can be seen throughout central Europe.

Of all the faunal groups, wild birds are the most useful indicators of environmental quality - because they are numerous and easy to see; and there are many different species, all with their own very specific habitat requirements and their own tolerance limits.

Recording and monitoring the birdlife in a woodland presents certain problems, however, because the vegetation hides many of the birds present.

There are four basic approaches to a woodland bird survey - and I will use a bird survey which I carried out in the Oak Glen in Glencree, Co Wicklow, this summer to illustrate these.

The first is the approach that would have been adopted by natural historians of old, and is still the way many casual bird surveys are carried out: that is, you simply visit the site on as many occasions as possible and note everything you see. This gives you a complete bird list, as well as a list of mammals, butterflies, flowers, or anything else that the surveyor is able to identify and record.

Casual recording like this, however, does not give you a proper idea of the actual numbers of the different species present. And you would need more exact information if you were going to monitor the changes in the bird community as the woodland developed from scrub to closed canopy.

The second method, then, is mapping, where you spend several weeks mapping out every single territory held by bird pairs in the plantation. As you can imagine, this would be exhaustive work. If every bird in the Oak Glen on a midsummer's day could be captured and then released in this room, it would be like a scene from The Birds. The room would be filled with thousands of small birds. The terrain in the Oak Glen is very rough, it has been ploughed up for planting, it is rocky, there is a lot of brambles and many holes and trenches. It is difficult enough to walk it, never mind record all the birds using it. Mapping is never more than 70% accurate anyway - you will always miss about 30% of the birds. And mapping would not be necessary except for research purposes, perhaps in a plantation of very high conservation value.

The other methods are the transect method and point counts.

The transect method is the easiest. I based a transect count on the method used in the Countryside Bird Survey, launched by BirdWatch Ireland and Dúchas this year, which is the same as the tried and trusted method developed by the British Trust for Ornithology for the British Breeding Bird Survey.

Basically, they survey 1km x 1km squares, chosen at random around the country. Two 1km long walks, parallel to each other, are carried out in each square. The 1km transect is divided into five 200m stretches and the birds seen or heard in each individual 200m are noted. Oak Glen is a little smaller than 1x1km, but the same principles apply.

This technique can easily be carried out in Oak Glen, as there are suitable footpaths one can follow. You go to the site in April or May, the time of year that the birds are nesting, and you go at dawn, 7.00am, to catch them in full song, during the dawn chorus, when they are most easily located and identified, and spend about 2 hours walking your transects. You do two counts, one in April and one in late May or June, the second count being carried out to pick up any late migrants that may have arrived later than April.

With point counts, you select, say, 10 points at random in your plot, using a map with a baseline grid of 20m by 20m squares. The points (or 20m x20m squares) chosen must be at least 150m apart so that you don't count the same birds twice, and you continue selecting points at random until this condition is met. You will have to spend 6 to 20 minutes at each point - decide how long beforehand - and count everything you see or hear from each point.

Point counts are useful because not only do you get an index of the abundance of each species in the wood, but you can also relate your results to the habitat at each point - and find which habitats are preferred by which species. The habitats within the woodland can vary dramatically.

But point counts are not easy to do in Oak Glen because of the roughness of the terrain. Nor is the plot size (65 acres) large enough to give you a sufficient number of 'hits' to make your results statistically significant, except for the most numerous species.

Unfortunately, the same applies to the transect counts I did in Oak Glen - they didn't provide a sufficient number of records for most species.

In all I made 16 visits to the site, comprising two transect counts, two point counts, one visit at dusk to look for crepuscular species, and 11 casual visits. I believe I obtained sufficient data to provide a comprehensive bird list for the site, as well as indices of abundance which, if not completely significant in all cases, will at least provide a good indication of trends.

I recorded 44 species altogether. Eight of these were casual visitors or 'fly-overs' such as Swift and Raven, which were not dependent on the site or nesting there.

There were 22 species nesting in the Oak Glen, while the remaining 11 species were nesting in other habitats alongside, such as the more mature woodlands and the riverbank. The edge effect: two habitats: the sum is greater than the individual parts.

Large and attractive species included Pheasant and Woodcock, both nesting in the Oak Glen, and Long-eared Owl and Jay, both nesting adjacent to the Glen.

The club of 22 species nesting in Oak Glen were comprised of thrushes, tits, finches, warblers, and some other common species.

The best indicator species were in my opinion the warblers. Perhaps unusually for such a small site, there were five different kinds of warblers nesting in the Oak Glen. I would like to compare the warblers to Darwin's finches in the Galapagos Islands, as they are all related but occupy different niches. But unlike Darwin's finches, these birds are not restricted to Ireland, they have very wide ranges, and they are all summer migrants, moving between Africa and Ireland every year.

At the moment, the willow warbler is easily the most abundant warbler in Oak Glen, nesting especially in the regenerating birch. (Number: about 30.)

The whitethroat is also quite common, (Number: about 12) while as many as six grasshopper warblers were heard in song on one count - quite a high number for this very skulking species which likes long wet grass and scrub.

The patch of mature trees provided the habitat for two pairs of Blackcaps, while the only Chiffchaff recorded occurred at the edge of the patch, on the perimeter of the Oak Glen.

As the woodland matures, however, the Grasshopper Warblers will disappear entirely, the Whitethroat will disappear too, but more slowly, while the Willow Warbler will probably occur indefinitely, so long as there are birch. Blackcap and Chiffchaff should increase steadily however. And many years from now, when we have a tall closed canopy of oak trees, there is a distinct possibility that another warbler, the Wood Warbler, will make an appearance. We may even see Lesser Whitethroat, though that is a remote possibility.

All of these birds are warblers and summer migrants, and documenting their future rise and fall in Oak Glen - and relating it to habitat changes - would make a fascinating long-term study.

At present it is difficult to compare results with other plots - so few plots have been surveyed in Ireland, and they vary so greatly. But as more and more plots are surveyed, we will accumulate a body of data and it will gradually become easier to see how much progress we are making with our new woodland plantations and our woodland conservation efforts.

Q & A Session

Noel Foley: You were mentioning that foresters took a long time to discover the environment, but I would also say it took environmentalists a while to discover plantation forestry in so far as it's only now, and some of this is being funded by COFORD, that environmentalists are studying the environment of plantation forestry, so it's not just one way it's a two way process.

Another comment I want to make, and I think you brought this out well yourself, is that it takes a long time to make a woodland. The birds that you are discovering there now apart from the mature copse, would have appeared if the place was fenced off anyway. They are feeding off the seeds of the vegetation that's growing rather than on the trees, it's going to take generations for a woodland to develop and I think that has been another problem in so far as people have studied mature woodland, canopy woodland and when they did not find the same species on the plantation woodlands there was a general air of disappointment, but the plantation woodlands, in terms of the journey through time, are only at the start of the journey. The Oak Glen is going to go on for centuries, it's only starting now.

Response: The Oak Glen is mostly open heath or scrub still, it's not really woodland as yet. All the species that I recorded are not typical woodland species, they are more birds of open heath and scrub. They are relying on the vegetation between the trees, like brambles, and actually I'm not sure if Coillte appreciate that fully, because in order to assist the Oaks to come along, they trample and spray in the middle of the breeding season,

Tony Cohu: May I ask are you going to continue the monitoring, and if so how often will you survey?

Response: From my point of view I thought that the transect method was the easiest to carry out because you only have to do two visits at dawn per annum. So I thought that either I would continue it every year or because it's such a straightforward system anybody could do it, so that we will have a record over fifty years if this same system is followed every year. I was looking for a system that could be repeated annually for this reason. All it takes is two visits of about two to three hours, one in April and one in May.

Linda Murphy: From the point of view of environmental assessment, you mentioned April and May were the best times to review the area. Would you say therefore that a survey taken in late autumn or winter was incomplete from a point of view of the birds present on the site?

Response: I did think that perhaps I should add a winter survey as well in order to be complete because you do get winter visitors that would not be there in the summer. But very few, basically some thrushes, redwings and fieldfares, so it would be a good idea to include a third visit, maybe in November, December or January to find out if there is any other differences at that time.

Noel Foley: I would have thought that two survey times would have been better than one survey time. But a thing that worries me a small bit is the fact that you are using the plantings along the roadways, is there not a danger over time, in so far as I presume over time in a place like the Oak Glen with nearby heavy centre of population you are going to get some level of human activity which could make the habitat along the roadways different from the habitat in the main body of the woods. Would this skew the results if you want to make a comparison over time.

Response: The disturbance factor I would rule out because it's a very lightly used place, not many people go there, surprisingly, and the birds are not affected by people just walking along, it's only if the people are actually pursuing them that they are likely to be affected, so the human element is not going to affect your results.

You are right though in that the paths are quite narrow so it's quite easy to see and hear what is on both sides of the aisles as you are going along, but I was simplifying things in my description. I actually climbed over the fence and walked down around the perimeter fence as well in order to make the progress slightly different, and thus get to see more species.