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The Harnham Water Meadows Framework Management Plan - Annexes

Annex XII. The Canada Goose (Branta canadensis)

A Discussion Paper For The Harnham Water Meadows Trust

John Vickerman, e-mail: jvickerman@onetel.com

Abstract

The Canada Goose (Branta canadensis) is a non-native alien bird species in the United Kingdom which, since it is generally a colonial feeder and breeder, can cause damage to the habitat it occupies through soil compaction, erosion and eutrophication. In addition, their large size and often aggressive nature tends to dissuade other bird species from feeding and breeding in the same habitat where the Canada Goose is present in significant numbers. A flock of Canada Geese up to 70 in number spends significant periods of time on the Harnham Water Meadows Site of Special Scientific Interest (SSSI).

It is proposed to manage this SSSI with a priority being the development of the site to become more suitable for encouraging lowland meadow bird species such as Lapwing, Curlew and Redshank to breed again on this site after an absence of around 40 years. To the better achieve this objective, it is likely that the Canada Geese will need to be eradicated from this site. This Paper discusses various methods as to how this may be legally achieved.

Given that the Canada Goose population is to be eradicated from the Harnham Water Meadows, it is then proposed that at least one suitably located and prepared shallow wetland “scrape” area is created to provide feeding and roosting opportunities for wading birds such as Lapwing, Curlew and Redshank – especially in the Winter months – with the hope that lingering birds in the Spring may stay to breed in the surrounding grass meadows.

The success of such a proposal to enhance and diversify the bird life of these meadows (plus the added benefits of providing additional habitat for the expansion of insect and other invertebrate diversity with an area of standing water), is likely to depend upon the removal of Canada Geese from the area plus meaningful control of other predators e.g. Foxes, Mink, Magpies and Crows on the Harnham Water Meadows SSSI.

The Canada Goose - A National Overview

The Canada Goose is not a native species of bird in western Europe having been introduced into Great Britain from the New World in about 1665.

Over the following 300 years Canada Geese became widely distributed mainly through the introduction of birds onto private estates throughout much of England. In the late 1930’s, the species began to live mainly in the wild, and by the 1950’s and 1960’s their impact began to conflict with farming activities.

Removal and translocation of birds to other areas during this time did nothing to reduce their numbers. On the contrary, translocation merely contributed to the general spread and increase in numbers through the 1970’s and 1980’s with Canada Geese becoming widely spread throughout much of the United Kingdom. From a population of less than 20,000 birds in 1970, the present UK population is now calculated through counting surveys to be in the region of 95,000 birds, and increasing at the rate of around 2% annually.

Age Longevity and Breeding Habits

Canada Geese have been recorded living in the wild for in excess of 24 years of age. However, the average life span would seem to be for around 6 years.

Breeding commences from 2 to 3 years old with 3 to 11 eggs being laid. Incubation lasts for 28 to 30 days and is carried out by the female bird. Female birds generally return to their natal areas to nest year after year regardless of whether their season is successful or not. So there seems to be a degree of predictability as to where some birds will nest.

Nesting takes place on the ground and usually occurs within 30 yards of water in loose colonial groups with island locations being favoured. Some birds though may nest up to half a mile from water. Most nests are sited at the base of a tree or in the shelter of a bush.

Due to the generally aggressive nature of the species, productivity is often high as a result of the bird’s large size and effective defence against predators at the nest and in defence of their newly hatched young.

Feeding Habits

Canada Geese are vegetarians feeding by heavy grazing of grass and other plant material including stems, roots, tubers, seeds and fruits.

At times, they will upend in water to graze on water plants and often completely uproot such plants from a water course, pond or lake.

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Canada Geese on The Harnham Water Meadows

Numbers

At present, there is a flock of around 60 to 70 birds which commutes mainly between the Harnham Water Meadows and the water meadows upstream on the River Avon north of Stratford Sub Castle, but the flock almost certainly frequents other parts of the River Avon valley water systems in the Salisbury area as well.

Impact of Canada Geese on the Harnham Water Meadows

The impact of colonial and flocking birds on a relatively small area can have a serious effect on the ecology of that area with water pollution and eutrophication being major potential problems.

Canada Geese are relatively heavy and have a large foot surface area thus causing crop damage, not just by consumption, but also by trampling, soil compaction, soil erosion and destruction of bankside vegetation of waterways.

The aggressive nature of Canada Geese can often dissuade other species of bird to feed or nest near to the Canada Goose’s preferred feeding and resting areas, and degradation of habitat caused by their presence in addition to the pollutive effects mentioned earlier, can reduce nesting and feeding opportunities for other species.

The Desirability of Removing Canada Geese from the Harnham Water Meadows

Too many of any one particular species in a given area will inevitably lead to the degradation of that area.

It is believed that the number of Canada Geese frequenting the Harnham Water Meadows is now causing, and is likely to cause further increasing levels of damage which may hinder the development and management of the Harnham Water Meadows as a Site of Special Scientific Interest (SSSI).

The effect of doing nothing about the presence of Canada Geese will be that, firstly, it will become increasingly difficult to expand the biodiversity of the meadows, and secondly, inaction is likely to hinder the reconstruction of the channel network of these ancient water meadows by the counter productive actions of the geese causing damage to newly restored waterways.

As an example, it is known that bird species such as Lapwing, Curlew and Redshank used to nest on the Harnham Water Meadows up until about 40 years ago, i.e. the mid 1960’s. All of these species have suffered large decreases nationally in their breeding populations since that time due to land drainage, loss of insect life and other negative habitat developments thus rendering former breeding sites to become unsuitable.

By sensitive management, it may be possible to encourage these species back to the Harnham Water Meadows. However, the presence of the Canada Geese by their ability to degrade a habitat and intimidate and chase other species away, then such unhelpful and damaging activity can only hinder the aspirations of the management in trying to encourage historical breeding birds back to the Harnham Water Meadows.

There can be no benefit to the future management of the Harnham Water Meadows SSSI and its biodiversity development, nor to the planned restoration of the ancient water meadow’s channel network by further toleration of the presence of a growing and damaging community of an alien species – the Canada Goose.

The Control and Possible Eradication of the Canada Goose from The Harnham Water Meadows

No matter how convincing and desirable the argument may be to support the removal of Canada Geese from the Harnham Water Meadows, to actually achieve this objective might be an extremely difficult, costly and time consuming exercise.

This is especially true of a species which is mobile and the offending flock spends a significant time away from the area of concern.

Therefore, what are the available options?

In such an urban area as the Harnham Water Meadows, it is unlikely that eradication by shooting is an acceptable option. Probably, control of numbers by the prevention of egg hatching would be the most acceptable method.

However, this suggestion has its own major failings in that some nests are likely to be off the areas that are intended to be under control, e.g. in areas surrounding the Harnham Water Meadows or adjacent to the River Avon north of Stratford Sub Castle or elsewhere, and thus may not be covered by the terms of any control licence.

It is possible, then, that this process may have no significant effect in reducing, let alone eradicating, the Canada Geese from locating on the Harnham Water Meadows.

It would seem, therefore, that given the likely negative outcome of any application to shoot the birds plus the dubious success of any egg control programme, so then the only other humane way of effecting the operation would be to trap and humanely despatch the birds – wherever they may be when in moult – when they are rendered flightless during June and July.

It may be that a combination of control measures incorporating both egg control and trapping may be the most efficient way forward.

A guide to the legal control measures in the United Kingdom applicable to the Canada Goose is enclosed for further information.

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Proposals for a development to encourage the return of some previously breeding birds, and to provide feeding and resting areas in a damp lowland habitat

The northern section of the Harnham Water Meadows east of the Town Path and bordered to the north and east by the River Nadder is a former area of working water meadows but which was cultivated at some time prior to and/or during the second world war. The effect of cultivation was to destroy the ridges and troughs of the former water meadows, and there are no plans to restore this part of the Harnham Water Meadows back to working water meadows.

However, it may be possible to use this area to create an additional habitat to the meadows designed to encourage the return of former breeding bird species such as the Lapwing, Curlew and Redshank.

In simple terms, the creation of a shallow “scrape” area permitting the creation of a shallow water area with low, raised islands and gently sloping edges could provide a semi-permanent wet area to the Harnham Water Meadows.

Scrape areas designed to attract wading birds need to be sited well away from surrounding hedges, belts of trees and wooded areas. Such birds require excellent all round visibility in order to feel safe from surprise by predators which may approach either on foot on the ground or airborne.

Proposed developments in locations affording favourable visibility from the perspective of such birds in a designated SSI are more likely to be viewed positively by any Agency that has to be consulted before any progress work can be carried out.

Such an area would have the following benefits for bird life on the meadows:-

1. Create a suitable habitat for wading birds to feed on soil invertebrates, and to act as a roosting area during the Winter.

2. Provide a wet area in Spring to encourage such birds to linger into the breeding season and thus may subsequently breed in the surrounding drier meadows.

3. Act as a habitat to encourage the breeding of insects and thus help to sustain a more diverse bird community.

4. Provide a favourable habitat for the development of young wading birds, and of other species, through the Summer and into early Autumn.

However, for such a project to meet these objectives, it would of course be necessary to carry out appropriate preliminary tests regarding the seasonal variations in the ground water table levels of that area.

The results of such an analysis may determine the desirability or otherwise of installing a pump to feed in, or pump out water from the scrape in times of dryness or to maintain appropriate water levels in wetter times.

Alternatively, it may be possible to feed in, in a controlled fashion and without the need for a pump, a water supply from a nearby feeder channel of the water meadows network, and to allow excess water to drain away naturally from the scrape area.

Major flooding on rare occasions of excessive rainfall in Winter is usually of only temporary nature and would be unlikely to cause permanent damage or loss of habitat to bird life.

Such a scrape area would need to be fenced so as to keep farm stock out of the newly created area, and such fencing would have to be of a kind that would minimise bird casualties from collisions with it.

For such a project to succeed, there would also need to be other control measures put in place:-

1. In an urban environment such as this, ongoing control of Foxes, Mink, Magpies, Crows etc:, all voracious predators especially to eggs and young of ground nesting birds, would be essential so as to improve the chances of success for targeted ground nesting birds.

2. And Canada Geese! Probably the most difficult of all to control effectively. A flock of 60 to 70 Canada Geese, and increasing, with access to a shallow scrape could almost completely negate the benefits of such a scrape area intended to enhance the bird diversity of the Harnham Water Meadows by their propensity to degrade such a habitat in such ways as already described. They would love it!

Unless ALL of these control measures could be effectively addressed, then it is questionable whether such a desirable scrape area should even be contemplated in the first place. The Canada Goose and its control is the key!

References

BASC (2005). The Canada Goose – A Guide to Legal Control Measures in the UK. Revised Ed., April 2005. The British Association for Shooting and Conservation.

C. Lever (2005) Naturalised Birds of the World T. & A. D. Poyser, 2005.

D.W. Snow & C.M. Perrins (1998). The Birds of the Western Palearctic (Concise Ed) by Oxford University Press, 1998.

C. Mead (2000) The State of the Nations’ Birds Whittet Books.

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