PatchBird
Nocturnal
Introduction
PatchBird Nocturnal is the nocturnal monitoring component of PatchBird Surveys. It extends the standard PatchBird approach to birds that are active, vocal or more readily detected during the hours of darkness.
Owls are the most obvious examples, but the nocturnal bird community is much broader. Nightjars, rails and crakes, some waders and other species may be considerably easier to detect at night. Nocturnal vocalisations can serve several functions, including territorial defence, pair communication and mate attraction. Other species may simply become more detectable when daytime activity and background noise have declined.
PatchBird Nocturnal follows the same basic principles as the main programme: defined and standardised survey effort, repeatable observations, complete reporting, and the recording of both detections and non-detections. The methodology differs where necessary to reflect nocturnal bird behaviour and the practical requirements of surveying after dark.
Methods
Nocturnal Survey Period
For PatchBird Nocturnal, the nocturnal survey period begins 30 minutes after sunset and ends 30 minutes before sunrise, based on local sunset and sunrise times for the survey location and date.
PatchBird Nocturnal Survey Types
-
Standard Nocturnal Survey — seven-minute stationary survey without playback
-
Playback Survey — seven-minute stationary survey with a maximum of two minutes of playback
-
Nocturnal Travelling Survey — purposeful nocturnal surveying over a larger area
Incidental nocturnal records are also accepted but are retained separately from standardised surveys.
Survey location
PatchBird's standard location rule also applies to nocturnal surveys. Each PatchBird location is based on the 1 × 1 km UTM grid. On the first visit, the observer selects the most suitable and safest permanent survey position within 300 metres of the mapped grid reference point. Once selected, the same position should be used for subsequent stationary surveys.
There is no requirement to stand directly on the mathematical grid corner. This flexibility is particularly useful for nocturnal surveys, when safe access may be more limited and many nocturnal birds are detected acoustically over considerable distances.
Survey duration
Unlike the 15-minute daytime PatchBird protocol, a standard stationary nocturnal survey lasts seven minutes. Field testing indicated little additional detection value from extending stationary nocturnal surveys to 15 minutes. A longer presence may also cause unnecessary disturbance around territorial or breeding birds.
Seven minutes provides a consistent sampling period while allowing sufficient time to listen for and record the surrounding bird community.
Nocturnal Survey Types
1. Standard Nocturnal Survey
The Standard Nocturnal Survey is the primary PatchBird Nocturnal protocol. The observer remains stationary at the selected survey position for seven minutes and records all birds seen or heard.
No playback is used.
The survey should represent a complete list of all birds detected during the seven-minute period, rather than only nocturnal target species. This includes birds flying overhead and any other species seen or heard during the survey.
If no birds are detected, the survey should still be submitted.
Non-detections
A zero count is a valid and important survey result.
Nocturnal birds may be present without calling or otherwise revealing themselves during a particular visit. Weather, season, breeding stage and individual behaviour can all influence detectability. A non-detection therefore does not demonstrate absence.
Repeated surveys build a history of detections and non-detections at a location. Over time, these data may allow patterns of occurrence, seasonal activity, site use and detection probability to be examined.
2. Playback Survey
Playback may be used to detect nocturnal birds that are present but remain silent. Territorial species, particularly owls, can respond rapidly to the call of another individual.
Because playback can influence bird behaviour, its use within PatchBird Nocturnal is deliberately restricted and follows a standard sequence.
Playback should only be used where the habitat is appropriate for the target species. It should not be used routinely at every survey location.
The recommended duration of using playback is as follows:
0–1 minute: Passive listening
Listen for all birds present. If the target species is detected during the first minute, do not use playback. Its presence has already been established.
1–3 minutes: Playback
If the target species has not been detected, playback may begin after the first minute and continue for a maximum of two minutes.
If the target species responds, stop playback. There is no need to continue trying to elicit further responses once its presence has been established.
3–7 minutes: Passive listening
No playback is used during the remaining four minutes. Continue listening and recording all birds until the seven-minute survey is complete.
Where possible, the survey record should distinguish between birds detected spontaneously and those detected during or following playback. The use of playback should also be stated in the checklist comments.
Responsible use of playback
Playback is a detection method, not the objective of the survey. The maximum playback period is two minutes, and repeated playback following a confirmed response should be avoided.
Responsive birds, particularly territorial owls, may react quickly, and there is little justification for continuing playback once a response has been obtained.
Observers must comply with national legislation, local regulations and site-specific restrictions. Playback should not be used where it is prohibited, where the habitat is unsuitable for the target species, or where there is a reasonable risk of disturbing sensitive birds.
3. Nocturnal Travelling Survey
PatchBird Nocturnal also accepts purposeful nocturnal surveys covering a larger area. These may involve walking, cycling or driving a route while actively looking and listening for nocturnal birds.
Records from travelling surveys may be associated with the nearest PatchBird grid point while retaining the actual observation information. Travelling surveys represent a different type of survey effort and are not treated as equivalent to seven-minute stationary surveys.
Incidental Records
Incidental records of nocturnal birds are also accepted.
Examples might include a Barn Owl encountered while driving, an owl heard from home, or a rail calling during an evening walk when no formal PatchBird survey was being conducted.
These observations can provide useful information about occurrence and distribution but are not treated as standardised PatchBird Nocturnal surveys. Incidental records are identified and retained separately.
Survey Safety
No bird record is worth taking unnecessary risks for.
Nocturnal surveys should only be carried out where observers can safely and legally stop, park or walk. Before beginning a survey, consider traffic, difficult terrain, water, weather, poor visibility and other local hazards. Wildlife may present an additional risk in some regions, while in other places walking after dark may be unsafe or inadvisable.
There is no requirement to leave your vehicle.
The PatchBird location rule allows a permanent survey position to be selected within 300 metres of the mapped grid reference point. Where appropriate, a safe roadside or parking location can therefore be selected rather than attempting to reach the exact grid corner.
A survey may be conducted from inside a safely parked vehicle or from beside it. The engine should be switched off and other sources of noise should be minimised.
Never stop where your vehicle could obstruct traffic or create a hazard for you or other road users.
Local knowledge and personal safety always take priority. If a location cannot be surveyed safely at night, choose another suitable position within the permitted area.
Background
PatchBird Nocturnal was developed partly from nocturnal surveys carried out over several years, including stationary listening, targeted surveys, travelling observations and field testing of survey duration and playback use.
These surveys helped shape the current protocol, particularly the seven-minute stationary survey duration and the restricted use of playback.
PatchBird Nocturnal provides a standardised way to include this otherwise easily overlooked part of the bird community within the wider PatchBird monitoring programme.