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Birds and Roads

Wilderness and Wildlife at Risk
10th January 1997

Lecture to the British Association for the Advancement of Science Within the John Mason Conference of the British Ecological Society on Monday 9 September @ 1415

Chris Mead, C. Biol., M.I. Biol.

Few conflicts in the countryside are as obvious as the pathetic bundle of feathers on the road surface that results from the collision of a bird with a car. However it is only recently that the consequences for whole populations of birds of such impacts, of road noise and of light pollution have become clear. I have spent a third of a century working for the British Trust for Ornithology, and review this subject from a personal perspective. I show how planners can take steps to alleviate the problems which may be caused by new roads. On existing roads apparently desirable features, like hedges, may cause widespread damage to local small bird populations. I argue that, under current legislation, planners have a legal requirement to take the effect on birds into account. This is certainly the case where roads are proposed near any sort of statutory reserve designated for birds or where rare birds are involved.

This version of what I said at the Conference is being posted a week after I gave the talk and has the references to the major work used. There will be a printed version of the major part of this talk, on bird casualties, appearing in British Wildlife (probably December issue). This is a serious bi-monthly magazine available from British Wildlife Publishing, Lower Barn, Rooks Farm, Rotherwick, Basingstoke, Hants RG27 9BG. The detailed road noise work has been published as a series of papers by Reijnen and his team. The practical handbook Predicting the Effects of Motorway Traffic on Breeding Bird Populations is available at DG25 from Road and Hydraulic Engineering Division, PO Box 5044, 2600 GA DELFT, The Netherlands. I have consulted widely with organisations like the BTO, RSPB, Wildlife Trusts, FoE etc. but this is a personal view.


I mentioned loss of habitat and the effects of fragmentation, of chemical pollution from exhausts, of chemical and oil run-off etc. in passing. One effect that many people may not know is of salt (Norman, Cross & Cockbain, 1981, BTO News, 114: 9). This caused the deaths of 680 Bramblings on a small stretch of road in Merseyside on 22 February 1981 when the melted water was the only unfrozen liquid around. Direct poisoning resulted and many intoxicated birds were run down (. Road lights disturb the birds and may cause birds, especially Robins, to sing at night. This does not seem to be a problem for the birds. The main parts of my talk will be about road noise and about death through impacts with moving vehicles.


Road noise is all pervasive and, at high vehicle densities, disrupts the communication between birds. This causes territorial behaviour to breakdown and can interfere with pair-bonding. The major recent work, proving the effects, has been undertaken in the Netherlands by Reijnen and his team. Major papers have appeared in the Journal of Applied Ecology (31, 95-101; 31, 85-94; 32, 187-202 and one other) and the handbook for planners has been referred to in the preamble.

Road Noise Effects in Woodland
10,000 Vehicles/Day detectable up to 1.5 km
60,000 Vehicles/Day detectable up to 2.8 km
Effects Detected for 26 of 43 Species Tested
Reduced Density Shown for:
Buzzard, Woodcock, Cuckoo, Tree Pipit, Garden Warbler, Goldcrest, Hawfinch, Chaffinch & 21 Other Species

Road Noise Effects for 45,000 Vehicles/Day Open Areas
80 kph Severe Effect @ 335 M
130 kph Severe Effect @ 730 M
Effects Were Detected for 8 of 12 species investigated.

Noise levels of 40 DBS affected Cuckoo & Black-Tailed Godwit but levels of 80 DBS were needed to effect Woodcock & Coot.
Road Noise Effects on Willow Warblers
1) Less Dense Territories
2) Fewer Experienced Males
3) Less Successful Breeding
4) Survivors Move Away Next Year
Effects Measurable to 2.8 km on Roads With 60,000 Vpd

These effects are carefully proved from the work done over several years. The territories in similar woodland at different distance from the roads were mapped. In years when particular species' populations were high the territories near busy roads were occupied but the birds in them were not able to breed.

This is not the only proven effect of road noise. For example there was a study of Grey Partridge in Westphalia (Illner, 1992: Gibier Faune Sauvage, 98: 467-480) close to and distant from a motorway. The density of pairs in spring near (300 m) the motorway was 0.8 Km2 but further away from the road it was as much as 3.0 pairs Km2 - noise levels ranged from 70dbs down to less than 40dbs (P<0.001).

Pathetic Bundles of Feathers

There is a long and honourable tradition of walking or cycling the roads to gather information on road deaths. It is a subject that has been neglected to a very large extent in Britain recently. However there is a lot of direct evidence as to the likelihood of birds being found on roads. This comes from ringing records and does not represent the actual chance of death of an individual bird being killed by traffic. The following are the recovery rates for British ringing for seven species of non-passerine, seven of passerine migrant and seven of resident passerine (Enjoying Ornithology, 1983, Poyser).

% Road Deaths (reports of British-ringed birds)
Kestrel 14.0%
Moorhen 13.3%
Lapwing 5.6%
Barn Owl 30.2%
Tawny Owl 31.0%
Kingfisher 15.7%
Green Woodpecker 13.6%
Sand Martin 18.9%
Swallow 9.8%
Sedge Warbler 18.4%
Lesser Whitethroat 18.1%
Whitethroat 22.8%
Willow Warbler 12.9%
Spotted Flycatcher 10.6%
Wren 15.1%
Blackbird 14.4%
Song Thrush 17.7%
Blue Tit 13.8%
House Sparrow 9.5%
Chaffinch 15.2%
Yellowhammer 28.7%

These results are matched by those from ringing in Germany for raptors and owls (Bairlein & Harms, 1994, Die Vogelwarte, 37: 237- 246):
German Ring Returns of Raptors & Owls
Goshawk 9%
Sparrowhawk 15%
Buzzard 26%
Kestrel 34%
Barn Owl 49%
Eagle Owl 40%
Long-Eared Owl 56%
Little Owl 62%
Tengmalm'S Owl 5%
Tawny Owl 54%

A careful study involving detailed territory mapping in Westphalia (Illner, 1992, 93-100: in The ecology and conservation of European owls. JNCC) tried to relate the apparent very high mortality through RTA (Road Traffic Accidents) with actual adult mortality.
Westphalian Owls a Detailed Study
10-15% of all Adult Mortality for Barn Owl & Little Owl
Crucial Speed for RTA 80 Kph (50 Mph)

Clearly owls are very vulnerable but the effect must be considerable as this study excludes young birds and we know that owls can be quite long lived. We should perhaps return to deaths of other species. As a result of some individual studies the BTO ran a Road Deaths enquiry from May 1960 to April 1961 (Hodson & Snow, 1965, Bird Study 12, 90-99). A total of 349 miles of road was covered regularly and 5,269 casualties of 80 species were recorded. Up to 177 deaths per mile were recorded and it was realised that even this was very much a minimum figure. We are also dealing with a bye-gone era when traffic flows were much less and very much slower.
BTO Survey 1960/61 (species 100+)
House Sparrow 2365
Blackbird 767
Song Thrush 461
Pheasant 284
Chaffinch 211
Dunnock 133
Robin 129
Blue Tit 104

Seasonal Distribution

House Sparrow total deaths: 2365

Blackbird total deaths: 767

More recently a two year study in Frankfurt (Wascher, Janisch & Sattler, 1988: Luscinia, 49: 41-55) covered 9.2 kms of urban and suburban road with speed limits ranging from 50 - 100 kph. A total of 687 birds were found dead with seasonal distribution as follows:


The species involved were Blackbird 277, House Sparrow 77, Warblers (10 Species) 57, Great Tit 45, Tree Sparrow 26, Blue Tit 22, Mallard 16, Robin 16 and a further 151 birds of 51 species.

In several of these studies it is clear that the mortality is mainly taking place when young birds are first meeting traffic. The learning curve can be seen in the results of Swallow mortality from British ringing. For the first month after leaving the nest 37.8% of recoveries are from RTA, for the next year it drops to about 12.7% and after one year has elapsed it reaches 7.3% (my own results some 15 years ago). However things can go spectacularly wrong as Estrada & Riera (l995, B. del Grupa Catala d'Anellament, 12: 17-24) showed for spring 1992 in the Ebro Valley of NE Spain showed. Bad weather led to the migrant hirundines being in poor condition and 512 hirundines were killed on 28.1 kms of road over three days. Swallows (307+) and House Martins (140+) predominated and being April 8 and May 5 and 6 we are talking about potential breeders.

The timing of mortality in the Blackbird deaths (and some other species) includes many in the first half of the year. Even the slow suburban roads are a danger then and particularly to breeding males during territorial chases. British ringing data show a clear bias towards males presumably for this reason. Of all recoveries 20.8% of males are RTA and the females are 12.8%. This is the same for Great Tits with 14.9% males and only 9.3% females. Incidentally not all species learn from experience and adult Bullfinches are more likely to die in RTAs than young - 14.2% rather than 7.1% (again my own data).

It is not just common birds that are affected. Habitat fragmentation of lowland heathland has had an appalling effect on several species. As if this were not enough the Dartford Warblers (Catchpole & Phillips, 1992, Biological Conservation: 61, 209-215) close to roads suffer losses during the breeding season which are, of course particularly serious as the bird's mate will also not produce young from the breeding attempt in process:

Dartford Warbler Holt Heath, Dorset
Adults Disappeared From Territories Including Roads
Losses Much More Likely Near Roads (P = 0.003)

Only 300 metres from my home a Hawfinch was nesting this May by a tiny country lane. It was being photographed by Chris Knights and the day the brood fledged the male was killed. Chris walked 100 metres down the lane and found another dead Hawfinch and three dead Chaffinch. Earlier I had found four dead Chaffinch at the period when young nestlings were being fed over 300 metres of the same lane! It is very unlikely that a nest deprived of food from one parent will succeed. And this brings us on to the environs of the roads and what causes the birds to come into conflict with the cars.

The lane involved with the Hawfinch and Chaffinch deaths is less than 4 metres wide and has vegetation up to the edge of the carriageway. Cars and lorries use it but the traffic load is small. Puddles form after rain and birds can be killed coming down to drink. More than 600 toads died one year on it and the death toll of rabbits, hares and Pheasants is enormous - even where the carriageway is between hedges with grass between them and the road. The lane comes up to the A1065 - a typical rural A road with traffic flows of 500 - 1000 VPH during working hours: probably in excess of 10,000 VPD. Its profile is not very good for the birds and I picked up a dead Barn Owl on it on the first Saturday in August (ringed as a nestling three months earlier 5 kms away). Two years ago 9 out of the 48 Barn Owl chicks we ringed locally died as a result of RTAs in their first six months. In 8 kms I have counted (from the car) 32 recognisable dead Pheasants in March and the lagomorph kills are sometimes even worse.

On a similar local road I chose a section of 100 metres where it crossed a shelter belt. One visit in late August to take photos for the talk produced several dead rabbits, one grey squirrel, a Chaffinch, a Pheasant, a Red-legged Partridge and a Tawny Owl on or immediately beside the tarmac.

Bigger and more noisy roads are not such a problem as the birds are not going to fly across so readily. This is possibly related to the width of the road in relation to the territory size of the small birds using the hedges. Typical territory radii in good habitat are 30 - 40 metres and roads covering approaching this width should not be a problem for small birds. They can be lethal for owls attracted to small mammals along the grass edges and management of these edges to discourage owls from hunting is crucial. Possibly allow rank vegetation to grow thickly is the best but more work needs to be done.

The magnitude of the problem is best illustrated by some official statistics:

Road Traffic in GB Billion Vehicle Kms
Motorways 63.3
Built-Up Major 77.9
Country Major 118.9
Minor Roads 150.5

The totals for previous years were interesting. The figures for 1990 through to 1993 were very similar (within 0.4%) but there was a build up over the previous years:


Have we reached saturation?

Road Lengths in GB Kilometres
Built-Up Major14,093
Country Major33,847

Average Vehicles/Day
Motorway 54,674
Built-Up Major15,144
Country Major9,624
Minor 1,314

These vehicles are now moving much faster than they were. The first new car I bought in 1966 had a brochure top speed of 68 MPH. Now the small car I have could cruise all day at 100 MPH. The increase in speed for cars and, particularly, larger vehicles has, I think, made the problem of RTAs much worse. I have made some guesses as to the total death toll:

The Total Death Toll On 365,000 Kms Of Road
@  30/KM 10,000,000
@ 100/KM 30,000,000
@ 200/KM 60,000,000

Total Annual Deaths of Vulnerable Birds
300,000,000 die each year
Roads3 - 20%
Cats20% ?

Many people get very uptight about the perceived damage that the increased population of Magpies does to their garden birds. These birds are seldom taking anything but eggs and nestlings who have only a small chance of contributing to the breeding population. Their cars are much more important and have provided the extra food, in the forms of wildlife dead on the roads, that have allowed the Magpies to increase in numbers. I am sure that late winter food shortages would, in a natural situation, keep Magpie populations regulated.

The Future

I think we should decide as a Nation that roads and the car should not be allowed to govern our lives and dictate the sort of countryside we live in. Where new roads have to built they should be planned in the farming areas with full and generous compensation for the farmers. Adequate land should be acquired to engineer decent wildlife refuges along them - as I have suggested.

There are two major initiatives that I would like to see. The first is that road noise and road deaths, as they may affect local statutory wildlife sites, designated for birds, and rare species on Schedule 1 of the Wildlife and Countryside Act, on the Red Data List or on the Red or Amber Lists of Birds of Conservation Concern MUST be taken into account by planners. Now it has been show that there are real dangers this is a statuary requirement under European Law and (I think) under PPG 9.

Secondly I am sure that we need to undertake very urgent research:

Urgent Topics for Research
The Birds
1)The Death Toll
2)Which Species?
3)Population Effects
The Vehicles
1)Reducing Noise
The Roads
1)How Do You Keep Birds And Cars Apart?

This research needs to be undertaken rigorously and extensively. An ideal undertaking for the BTO. For my own part I am in the process of marking out the road outside the house here (A1065) and the lane where the Hawfinch died with marking to allow me to plot deaths accurate to a metre or two. I will then be walking the road at least once every three days to try to relate the deaths of birds and other animals to the physical surroundings of the road.

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