Environmental Engineering Reference
In-Depth Information
differences in behaviour between adult and juvenile falcons, the adult male and a
juvenile female falcon (offspring of the adults) was radio tracked during the
2010/2011 summer. The male was tracked for 5 days in each of December 2010 and
January 2011 while the juvenile female was tracked for 2 days in each of January,
February and March, 2011.
Data were collected using triangulation at four fi xed high point tracking stations
that provided optimal 360 0 line-of-sight radio reception (Barea 1995 ; Seaton 2007 ).
Radio tracking was undertaken during the post-breeding period in autumn/winter
(Tracking period 1; March to July 2010) and during the summer breeding season
(Tracking period 2; December to March 2011). The adult male was tracked during
all periods, the adult female during the fi rst tracking period and the fl edgling female
during the second tracking period. Sampling effort comprised tracking each adult
bird for 10 days (consisting of 2 days per month) over the respective tracking periods,
with radio fi xes recorded every 10 min over an 8 h day with sampling effort over the
study period varied across daylight hours. In order to ensure that 10 days of tracking
was suffi cient for this study, cumulative area use plots using Biotas 2.0 - Ecological
Software Solutions™, were generated to check cumulative home range area
asymptotes had been reached, thus supporting the adequacy of sampling effort.
Radio tracking data were transcribed into Excel spreadsheets and fi ltered to
extract data that enabled an analysis of each falcon for each study period. The loca-
tion of each falcon at the time of each 10 min fi x was estimated using LOAS 4.0
(Ecological Software Solutions™). LOAS 4.0 converts the bearings obtained by
radio triangulation into locations by fi nding the most likely estimate for a falcon's
location given the average of the co-ordinate points for the observed set of bearings.
The locations for individual falcons were pooled across the study period to refl ect
the respective season for the analysis. These data were then analysed in Biotas 2.0
to produce home ranges with a kernel estimator (Worton 1989 ) using least squares
cross validation Seaman and Powell ( 1996 ). 95 %, 75 % and 50 % kernels were
produced for each falcon. The kernel method considers the variation in the data
rather than evaluating each point in isolation from others, thus providing unbiased
estimates of the probability of occurrence of different areas (i.e. kernel contours)
within a home range. This is important when examining home ranges in the spatial
context of features on interest, e.g. habitat types or proximity to turbines. An additional
utility of Biotas 2.0 is that outputs are optionally generated as shape fi les and can be
imported directly into GIS software. These contours were mapped in GIS over a
habitat layer depicting previously mapped vegetation classes.
Although there are rare occurrences of raptors colliding with towers, falcons
are principally at risk of collision when fl ying within the rotor swept area (RSA).
To assess the amount of time falcons spend fl ying within the RSA, fi eld ecologists
undertaking the tracking study also observed and recorded all falcon behaviour,
including fl ight heights of the birds under study referenced to known heights of
onsite wind masts, so that the proportion of time spent fl ying within the RSA could
be calculated.
Search WWH ::




Custom Search