Download presentation
Presentation is loading. Please wait.
1
Crepuscular Ducks Low light movement of waterfowl in inland water bodies of North Carolina Brian Bockhahn 2015
2
Hypothesis questions Do waterfowl roost on inland lakes at night during migration, and to what extent? Do waterfowl move around inland water bodies during low light periods? What light levels are optimum for movement? Which species move around and do they show light level preferences? Implications on bird counts and surveys.
3
Where? Christmas Bird Count (CBC) sites
Falls Lake Jordan Lake Kerr Lake Roanoke Rapids Lake Lake Phelps Swift Creek
4
Where? CBC sites
5
Falls Lake - COE North of Raleigh, east of Durham 12,000 acres
Depth 20-30’ 26 miles long 175 miles shoreline Widest point 1 mile Flood control, water supply, wildlife habitat, and recreation Elevation 251 msl
6
Jordan Lake - COE Southwest of Raleigh 37,000 acres Depth up to 30’
18 miles long 200 miles of shoreline Widest point 1.7 miles Flood control, water supply, wildlife habitat, and recreation Elevation 216 msl
7
Kerr Lake - COE Border of NC and VA north of Henderson 50,000 acres
Depth up to 130’ 34 miles long 850 miles of shoreline Widest point 2 miles Flood control, water supply, wildlife habitat, recreation and hydroelectric power Elevation 296 msl
8
Roanoke Rapids Lake - Dominion
4,600 acres Depth up to 62’ 8 miles long 47 miles of shoreline Widest point 1.25 miles Flood control, water supply, wildlife habitat, recreation and hydroelectric power Eleation 132 msl
9
Lake Phelps – second largest natural lake
Crewsell, Washington county NC 16,600 acres Depth up to 9’, average 4.5’ 6 miles wide 20 miles of shoreline Natural lake, pocosin Elevation 132 msl
10
Swift Creek Northeast of Rocky Mount Flows into Tar River
12 miles long slough Natural river, beaver swamps, some green impoundments for waterfowl Elevation 75 msl
11
How? Sky Quality Meter Measures sky brightness
Magnitudes per square arcsecond Site to site, day to day 80 degree cone, with direction of angle important
13
SQM compare to actual TOD
SQM Reading 508 Sunset – 7 SQM 541 Dusk 13 SQM Time of Day - PM
14
SQM 6
15
SQM 7
16
SQM 8
17
SQM 9
18
SQM 10
19
SQM 11
20
SQM 12
21
SQM 13
22
SQM 14
23
SQM 15
24
SQM 16
25
SQM 17
26
SQM 18
27
Data collected Date Location Temp Cloud % Weather Base reading
Both dawn and dusk Flat reading Each sighting Time of day SQM reading Quantity Species Direction of flight
28
Identification techniques
Flight profile Flight styles Flock patterns Call notes, flight sounds
29
Data – species detected
Canada Goose Wood Duck*** Gadwall** American Wigeon American Black Duck*** Mallard*** Blue-winged Teal Northern Shoveler Northern Pintail Green-winged Teal Double-crested Cormorant Canvasback Scaup sp Bufflehead Hooded Merganser*** Red-breasted Merganser Ruddy Duck American Woodcock Display
30
Crepuscular Ducks Data Sheet
Date: 1/3/12 Time: PM Location: Kerr Lake Dam Temp: 36 Clouds: 80% Weather: cold, light south winds TIME SQM QTY SPECIES DIRECTION OF FLIGHT 450 5.0 FLAT READING 455 6.2 5 HOODED MERGANSER SW OVER DAM 506 6.4 3 SW OVER DAM 5 2 515 7.6 2 516 7.8 3 518 8.1 525 9.5 527 9.9 6 529 10.5 8 531 10.7 12 MALLARD HOODED MERGANSER 29 AMERICAN BLACK DUCK 14 24 AMERICAN BLACK DUCK 533 11.2 NORTHERN SHOVELER GADWALL
31
Light levels SQM chart Total Waterfowl Dusk 13 SQM Sunset – 7 SQM
SQM Reading
32
Species to SQM significant correlations
33
Peak Flights by SQM SQM Reading
34
Implications Bird Surveys – Pre-dawn and Post-dusk are important times to be in the field to survey for waterfowl. Migration pathways/flight lanes can be discovered or explored and should be monitored. Dams, rivers, lake coves and widest water body points. Surveying at peak times will increase accuracy of population estimates.
35
Conclusions Waterfowl regularly roost/stopover for night on inland water bodies. Waterfowl do move around and low light levels with peaks in the SQM range. just before to after dusk before to just after dawn. 10 species of dabblers and 7 species of divers were detected and some do have light level preferences. Optimize time for best survey/inventory results.
36
Further considerations
Daily monitoring to assess change throughout the season. Different numbers each night? Do they migrate to feed and then return to roost again or just stop over for a night? How does wind and weather influence low light flights? Freezing conditions play a role? Does flock size play any role in light preference? Collect yearly data. Is there any preference to dawn vs. dusk?
Similar presentations
