Presentation is loading. Please wait.

Presentation is loading. Please wait.

Two bat schemes that didn’t make it NL 1990-1999 Rombout de Wijs.

Similar presentations


Presentation on theme: "Two bat schemes that didn’t make it NL 1990-1999 Rombout de Wijs."— Presentation transcript:

1 Two bat schemes that didn’t make it NL Rombout de Wijs

2 Schemes for monitoring bats Hibernacula Colonies/summer roosts Point & line counts for passing bats Transect counts advertising bats

3 Schemes for monitoring bats Hibernacula Colonies/summer roosts Point & line counts for passing bats Transect counts advertising bats

4 Point/line counts transects non-random selected (near home) 1 main type of habitat 4 km (walk) to 15 km (bike) 20 points and 20 lines in between minimum distance between points 200m (walk) or 400m (bike) points close to water if possible at least some suboptimal points

5 Transect 7: Schaep & Burgh

6 Point/line counts detector tuned to 42 kHz 3 minutes at points variables at each point/line: –presence –maximum –total # passes start at hr after sunset temperature > 8°C

7 Point/line counts counting each month April-September in middle of month (10-20th) since 1997 only in May, July and August and only at points

8 17 transects in total mainly central NL

9

10 Number of counts/year

11 Species observed at transects

12 More details methodology (results from the 1999 paper) variables strongly correlated, but sum of passes showed much variation. Risk of saturation in presence results points and lines strongly correlated, but variation lower at points no difference in indication value of mean and maximum value per season species showed different seasonal variation, therefore 3-6 counts necessary: later analysis showed 3 counts sufficient number of transects needed is 100 for detecting differences between years of 20-40%, but rule of thumb CBS adopted: transects for detecting trends over 5-10 years (for each stratification layer)

13 Trends 6 species using model TRIM and using variable Presence

14 Why giving up? insufficient # transects insufficient # volunteers, in spite: –much effort to arouse interest (newsletter, talks) –making field work easier: only in 3 months (was 6) and only at points (was including lines) financing stopped Scheme abandoned

15 Schemes for monitoring bats Hibernacula Colonies/summer roosts Point & line counts for passing bats Transect counts advertising bats

16 Schemes for monitoring bats Hibernacula Colonies/summer roosts Point & line counts for passing bats Transect counts advertising bats

17 non random selected (near home) km walking or cycling at 5km/hr 6 counts 15 Aug Sept. start 1 hr after sunset temp. > 8°C detector tuned to kHz, Pnath checked at 40 kHz (for 2nd part of call) observations drawn on maps

18 Transect counts advertising bats end of season: clustering observations to “territoria” when flying: different individual when >100 m variables: –maximum at 1 count during season –mean of counts during season

19 41 transects in total 23 counted 3 years or more

20 mostly transects 3 area’s mostly urban

21 first 2 years experimental several 1-2 years only

22 species present in 41 transects

23 results from Pnath and Nnoc inaccurate results from Ppip better trends similar to PLC

24 Why giving up? insufficient # Nnoc insufficient # volunteers does not add much to PLC financing stopped Scheme abandoned

25 Should we restart “PLC”? need of monitoring data on Nnoc and Pnath need of data other species in summer, especially when not counted in colonies

26 in 1996

27 Better prospects now? Atlas project longer ago, so more motivation? better awareness of need of data?? better methods? –easier, so more volunteers? –less variation, so less counts needed? –better equipment, automatic registration?

28 New methods, new discoveries? Let’s face the challenge of a new start!


Download ppt "Two bat schemes that didn’t make it NL 1990-1999 Rombout de Wijs."

Similar presentations


Ads by Google