Monitoring of Vanuatu Scrubfowl burrows at Kurumambe, Tongoa, Vanuatu VEAN
Location of Scrubfowl colonies monitored at Kurumambe, Tongoa
Location of monitored burrows on Kurumambe West Coast, Cliff side North west coast.
Operating times of trial cameras at Kurumambe, Tongoa. • 12 cameras were set – 1 of A8 which, A8, only operated B7 B9 successfully on the first day. This Burrow Location and Number A3 camera is not included in B13 A4 subsequent assessments. B5 • Other cameras worked for B2 A10 between 50 and 495 days B12 between 19 th November 2016 A11 A6 and 28 th March 2018. 0 50 100 150 200 250 300 350 400 450 500 No of Days active Nov-16 Dec-16 Jan-17 Feb-17 Mar-17 Apr-17 May-17 Jun-17 Jul-17 Aug-17 Sep-17 Oct-17 Nov-17 Dec-17 Jan-18 Feb-18 Mar-18
The number of Camera-days, by burrow, captured during the study period. • No of camera-days per month 300 A6 A11 B12 A10 for the study period. B2 B5 A4 B13 250 A3 B9 B7 A8 • Down arrows indicate dates 200 when cameras were reset. Camera days 150 • Camera A6 can be seen to have operated continuously 100 throughout the study period, 50 while A11 was continuous for 12 months from November 2016. 0 Month
Diurnal variation in sightings of Vanuatu scrubfowl at nesting burrows in Kurumambe • Scrubfowl are diurnal (a 160 surprising finding)– but with a 140 peak in sightings in the first 3 120 hours after sunrise. 100 No. of birds • Cameras were active continually 80 throughout night and day. No 60 sightings of scrubfowl between 40 19.00hrs and 03.00hrs the next 20 day. 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Note that time of day is based on first time that bird was observed at site, even if length of Hour of Day observation extended over more than 1 hour.
The number of Vanuatu scrubfowl recorded on camera by burrow. • Data presented by colony and by 2.0 0.200 burrow. Colony A is on the western cliff, Colony B on the north west cliff. • Markedly more birds at burrows 6 and 1.5 10 in Colony A. This is also where Laying attempts per day most laying attempts were reported – Birds per day 1.0 0.100 although burrow 13 at Colony B had similar rate of laying. • Note that there is a 10-fold difference 0.5 between number of birds and number of laying instances. Bird numbers (n=1115) are based on assumption that a new occurrence is reported when there is a 0.0 0.000 minimum 10 minute gap between sightings on image. B12 B2 A11 A3 A4 B9 B5 B13 A10 A6 Laying events (n=71) are based on assumption that birds need to spend a minimum of 10 minutes in Burrow location and number continuous view at the burrow.
Variation in numbers and frequency of laying through the year. • Peak laying period between June 1.50 0.15 and August – although high numbers also present in December. 1.00 0.10 Laying events per day Birds per day • Laying periods recorded throughout the year. 0.50 0.05 • Variation in bird numbers at sites mirrors laying dates. 0.00 0.00 Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Bird/Day Lay/Day
Between year variation in time spent at 1 burrow. • No. of birds recorded was 141 138 No of observations similar, but time spent, and number of times >10 minutes at 2016/17 2017/18 Year the site was higher in 2016/17 10 Observations >10 mins than 2017/18. 6 • Local assessment was that there were more birds in 2017/18 than 2016/17 2017/18 Year 2016/17 – not supported by this 5:37:45 AM evidence. Observations Length of 3:38:38 AM Data based on continuous camera activity at 1 site (A6) from 19 th November to 27 March in both years. This was the only site where significant coverage in both years was achieved. It was the site with most numbers, and highest occurrence rate of scrubfowl on the site. 2016/17 2017/18 Year
Timing and distribution of rat records, as recorded by trail cameras at Kurumambe • There were 131 observations of 20 rats during the study period. No of Occurrences 15 • Rats were recorded at 9 of the 11 10 operating camera traps. The 5 number of rats varied between 0 sites – with, maybe, more at the 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Hour of Day North west than the western site. 33 • Rats were exclusively recorded 35 30 during the nocturnal hours – No Rats /100 days 25 between 18.00 and 05.30hrs. 20 20 • Most rats appeared to be R. 15 12 10 exulans – but ID from images is not 5 2 2 reliable. 1 2 0 0 0 0 0 B2 A11 B12 A10 A4 A3 B7 B13 A6 B5 B9 Burrow location and number
Timing and distribution of cat records, as recorded by trail cameras at Kurumambe. • There were 208 observations of 25 20 cats during the study period. No of cats 15 • Cats were recorded at 9 of the 10 5 11 burrows monitored. There 0 0 1 2 3 4 5 6 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 may have been more cats at the Time of Day (hours) Western than the North Western 30 25.9 colony. 25 No Cats per 100days 20 • Cats were recorded at all times 13.9 15 13.3 of the day – but with, maybe, a 9.1 10 7.5 peak in the hours before dawn. 3.8 5 1.9 1.6 0.6 0.0 0.0 0 A3 B7 B5 B2 B12 A11 B13 A10 A4 B9 A6 Burrow location and number
Conclusions - 1 • Scrubfowl were recorded at 10 of the 11 burrows that were monitored – with behaviour indicating laying attempts being recorded at 4 of these burrows. • Laying attempts were recorded on 1 in 10 days at the 3 most actively used sites. Co-incidentally this is thought to be the laying rate of a single bird – 1 egg every 10 days. • There are peaks in birds and laying behaviour in the months of June, July and August – while there is a suggestion of a second peak at the turn of the year, December and January.
Conclusions - 2 • The two principal predators at the site are likely to be cats and, possibly, rats. • Cats are known to be effective predators of scrubfowl chicks – and cameras here recorded cats watching burrows at all times of day, possibly to capture chicks as they dig their way out of the burrow. • Most rats seen appeared to be R. exulans – which is unlikely to be a significant predator. One or two images may better fit R. rattus – so this needs to be investigated further. • We saw few other, significant predators of scrubfowl at the site – although Swamp Harrier is often seen quartering over the site.
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