The potential disturbance to wildlife

Impacts on birds

The effect of disturbance

The impacts on cetaceans and mammals

The relative importance of recreational disturbance

Impacts on Birds

There is a large degree of uncertainty over the results obtained from long term monitoring and research into the causes and effects of waterfowl disturbance. Due to the large number of variables which are involved and the degree to which each is observable, it is often difficult to assess the naturally occurring factors, such as the weather, which affect bird numbers in isolation from human influences. Furthermore, the complex ecological factors affecting waterfowl numbers are not always fully understood and may not even be apparent to an observer. Such interaction of natural and human influenced factors complicates the analysis of the long term effect of recreation.

There are a number of potential sources of direct disturbance to waterfowl from water-based craft including:

• Speed
• Sound
• Size
• Visual Intrusion
• Characteristics of Craft Movement

It is important to bear in mind, therefore, that disturbance is not related only to sound but also to visual presence. Therefore where waterfowl have a propensity to be disturbed, sailing, human-powered and motorised craft all have the potential to cause impacts.

The Effect of Disturbance

The effect which disturbance has on waterfowl varies greatly between the different species of bird and also depends upon the size and characteristics of the water body and the availability of alternative sites. Different species of birds react to disturbance in different ways and their sensitivity varies throughout the year depending on their specific activity at each location. Breeding and overwintering waterfowl are particularly sensitive to disturbance. This usually coincides with reduced intensity of recreational activities. However, it is important to note that some wintering waterfowl may begin returning as early as August, particularly if there has been a poor summer in the Arctic.

Depending on the magnitude of the disturbance, some birds may take flight temporarily, but return after the disturbance ends. Other birds may modify their feeding habits, whilst more sensitive species may suffer reduced breeding success or, ultimately, desert the site. When a bird is forced to take to the wing, energy intake ceases and energy expenditure greatly increases. At times of limited food supply and/or cold weather this could be life threatening for certain species. Where disturbance causes a bird to desert a particular site, the availability of suitable alternative sites is critical for the bird’s survival. Furthermore, the site in which it settles may already be populated or may be of lower quality resulting in lower rates of energy intake.

In summary, the disturbance may result in:

• Disturbance effects - which can be temporary but may have impacts on feeding, resting and energy intake of the bird
• Significant population impacts - which can impact on local and national populations of particular species

Disturbance which results in permanent long term impacts on bird populations is generally of greater national importance than short term localised disturbance.

Impacts on Cetaceans and Mammals

Dolphins and porpoises frequently appear to be interested in human activity and will readily approach boats. For example, at Fort George in the Moray Firth, bottlenose dolphins readily come to boats, to bowride or just to escort them through the narrows. The resident population of bottlenose dolphins is northern Europe's biggest colony but there is now a concern that the increasing number of boats within the Firth could pose problems in the future. Engine sound and erratic manoeuvres can distract feeding dolphins and may even drive them away from the area. Aberdeen University in collaboration with Scottish Natural Heritage has produced a code of conduct for boats in the Moray Firth. Guidelines for minimising the impacts of recreational activities have been produced by DETR (1999).

Where boating takes place in the vicinity of seal colonies, it has the potential to cause disturbance. In particular, the presence of craft in shallow coastal waters frequented by seals or in the vicinity of haul-out sites can cause disturbance. The potential disturbance to seal pups is also important and may include disturbance at feeding and resting times and enforced separation from their mother.

The Relative Importance of Recreational Disturbance

It is extremely difficult to assess the impact of boating-related wildlife disturbance in isolation from other sources of disturbance, both natural and human influenced. Wildlife may be disturbed not only by the boats themselves but also by the participants, particularly where the boats allow the users access to sensitive habitats.

As noted above, all types of craft have the potential to cause disturbance, whether wind, human or engine powered. It is very much at the local site level that the causes and effects of disturbance can be observed. It is also important to note that some disturbance studies have indicated that sailing may cause more disturbance at a national level than powered craft for the following reasons:

• -sailing is a more widespread activity
• -it occurs at most of the sites where bird counting takes place
• -there is a relatively high level of winter activity
• -participants spend a large proportion of time on or near the water.

However, it is the effects of a disturbance at a local level, which is of relevance to site-specific management responses.

Motor boating and water skiing activities take place in relatively fewer locations than sailing and are less intensive in winter. Personal watercraft, on the other hand, can operate in shallower water than many sailing craft and their engine sound can add to any potential disturbance. However, there has been little research carried out into the impact of this disturbance. Small craft such as canoes and rowing boats may also cause disturbance in areas which are inaccessible to larger craft.

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