Download M02 D03 Introductory slides ppt

WALLACE RESOURCE LIBRARY
Module 02 – Survey Techniques:
D03 – Comparison of bird survey techniques
Why Survey Biodiversity?
• Global decline in biodiversity
• But how do we know?
• In order to assess biodiversity we must apply appropriate
survey techniques
• This provides the information we need to understand what is
happening to biodiversity on a local as well as a global scale
Why Survey Biodiversity?
• IUNC Red list of Threatened Species
Extinct (EX)
Extinct in the Wild (EW)
Critically Endangered (CR)
Endangered (EN)
Vulnerable (VU)
Near Threatened (NT)
Least Concern (LC)
How do we Survey Biodiversity?
• Global or National scale
- Satellite images
• Local scale
-Capture-Mark-Recapture
-Transect and Distance sampling
-Passive trapping
-Camera trapping
-Direct counts e.g. Helicopter surveys
Why are birds important?
• Birds often used for as indicators of ecosystem health :
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Taxonomically well known
Abundant and apparent
Large samples easy to obtain in order to look at variation
Predictable, rapid and linear response to disturbance that
can be analysed
– Bird abundance and diversity closely associated with other
species and ecosystem resources
– Relatively unaffected by seasonal variations
Point counts
• Suits dense habitat such as forest and scrub
• All birds available for sampling, including more cryptic, shy
species
• Suits species-rich habitats such as tropical forest
• Time is lost moving between points, but counts give time to
spot and identify shy birds
• Double counting birds is a concern within the counting period
• Birds may be attracted to the presence of observers at
counting stations
Mist netting
• Only surveys birds that occupy the lower canopy
• Additional data can be collected (e.g. weight, sex)
• Ideal when dealing with birds that are hard to identify from
sight or vocalizations
• Suitable for all terrestrial habitat types
• Requires trained bird handlers
Methods
• Survey took place in Cusuco National Park, Honduras
• Surveying to help manage and conserve forests in
Honduras for bird species
• Need to discover which species occur in the forest
• 70 hours spent on point count surveys
• 400 hours completing mist netting surveys
Research questions:
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Which of the two methods (mist nets or point counts) do you think is the most efficient
for surveying birds in Mesoamerican cloud forest?
•
Comparing the methods:
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At any particular point, which method detected the most species?
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Do the two methods detect the same kinds of birds?
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Can you give examples of the kinds of birds which mist-nets are better at surveying
than point counts, and vice versa?
•
Recommendations:
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Which survey technique should be the main methodology for the planned largescale survey of Honduras’s cloud forest?
–
If the time is available, would you recommend the other method as an important
secondary technique? If so, why?
Summary and conclusions
• Point counts more efficient
• Mist nets only survey
understorey birds
• Point counts primary method
• Mist netting secondary
method