Reports

1997 Duck Banding Effort at Lewis River Slough, Susitna Flats

State Game Refuge, Upper Cook Inlet, Alaska.

U.S. Fish and Wildlife Service, Division of Migratory Birds.

September, 1997

INTRODUCTION

Yet another year of banding was added to the upper Cook Inlet contribution to the "5-Year Cooperative Program for Pre-season Banding of Mallards and Pintails in the Pacific Flyway". This makes it the eighth consecutive year of banding in upper Cook Inlet. Duck banding was initiated in 1990 by the U.S. Fish and Wildlife Service (FWS) and the Alaska Department of Fish and Game (ADF&G) to, ultimately, determine the origins of mallards and pintails harvested in the Pacific Flyway. Banding at Lewis River Slough (LRS) was conducted by ADF&G from 1990 to 1993 (Rosenberg 1990, 1991, 1992, 1993); FWS personnel have operated the camp for the subsequent four years.

STUDY AREA AND METHODS

The Lewis River Slough is located on the western side of Cook Inlet approximately 27 miles west of Anchorage, Alaska. The area is characterized by numerous, shallow open water brackish marshes with abundant aquatic vegetation. Trap sites were characterized by shallow water (10 - 30 cm), a relatively firm mud bottom and submerged wood. Sago pondweed (Potamogeton pectinatus) was common throughout the marsh as were emergent sedges and reeds.

On 31 July FWS personnel erected 7 (4 welded wire Medicine Hat, WW, and 3 PVC panel, PVC) traps in the marsh in the LRS marsh on the south side of the Ivan River (Figure 1, see Rosenberg 1990 or Balogh 1993 for details of trap designs). Six (2 WW and 4 PVC) traps were placed in the marsh, per previous years, to the N of the Ivan River. Traps were baited with whole barley and left open for a day to allow ducks to enter and exit freely. Traps were closed (operational) on 1 August and banding began on 2 August. Traps were added (2 PVC traps were stolen the first day from the N marsh) and moved in subsequent days (see Figure 2). In the south marsh, one WW trap was moved and placed next to another that was doing extremely well (they both continued to do well). Most traps were located within a few meters of shore. Trap entrances were oriented toward likely avenues of travel for feeding ducks and toward the canoe approach (to keep birds from flushing toward the vulnerable funnel area-they sometimes swim under it; some were adjusted after initial setup). All traps were checked once daily, starting at 10 a.m. with those located in the LRS marsh. It took between 3 and 5 hours, varying with capture numbers, to band and release ducks, record data, and rebait these traps. A canoe was used to travel between traps. Two more canoes were used to cross the Ivan River and for travel between traps on the northern marsh. These traps were checked daily in mid-afternoon. These also required between 3 and 5 hours to process, depending on the number of ducks captured.

Trapped ducks were herded into a wire catch box placed directly against the exit hole in the trap. Catch-boxes varied in size (see recommendations) and were equipped with a trap door that could be shut with a pull cord. Small, elastic "bungee" cords were attached to both the trap and the catch box to pull them together, and to adjust for different exit hole dimensions and water depths (Figure 2). Birds were either taken directly from the catch box and banded or, when we had large numbers in the large, unnetted catch box, were placed into a large cloth bag prior to banding. This kept the ducks from beating wings and bill against the wire mesh (one major source of injury) and appeared to calm them. All traps have exit holes with doors that swing up and down except for one PVC which was not converted (and is still a slit in the nylon netting which needs to be laced up each time). Trapping ended after trap checks on 19 August.

RESULTS

Thousands of ducks were observed feeding and resting in the LRS vicinity. Smaller numbers of large waterfowl particularly white-fronted geese, Canada geese, and trumpeter swans were also observed. Fifty bird species were recorded over the 20 day stay at LRS (TableX).

Banding Success: During 20 days of trapping, 13 traps and 239 trap-days, 751 ducks were captured, banded and released. Eight species were captured and banded: mallard, northern pintail, American green-wing teal, northern shoveler, American wigeon, greater scaup, gadwall and common goldeneye (Table 1). Northern pintail, mallard and green-wing teal accounted for 96.5% of all birds captured and banded; pintails were, by far, the most common (490, 126 and 109 individuals, respectively, Table 2). The average capture rate of 3.1 unbanded ducks per trap-day was higher than the rates of 1993, 1994 and 1996 (2.3, 2.5 and 2.5 respectively; 1995 trap-day data are unavailable but was the poorest year ever, Table 3). The only exceptional result for the 1997 banding effort was the number of pintails banded, which was more than twice the number banded for any previous year (Table 3.). About 87% of the pintails were hatch-year (HY) birds; 58% female. The 13% after hatch-year (AHY) pintails were also 58% female. Only 5 locally hatched pintails were captured. About 84% of the banded mallards were HY (55% female). As in previous years only a very few local birds were banded in 1997 (12 ducks, or 1.6%). See Appendix 1 for banding schedule.

Injury/Mortality: Trap-induced mortality was slightly higher than last year (2.7% vs. 2.1%) and consisted of 16 pintails, 2 green-wing teal, 1 local scaup and 2 greater yellowlegs. Two teal were found dead after forcing their heads through the welded-wire trap mesh. Most mortalities were found floating inside traps without an obvious cause of death. There were numerous minor injuries, primarily abraded wings and culmens. Most of these were associated with welded-wire traps.

Recapture. Around 317 ducks were recaptured: mallards 32, pintails 273 and green-wing teal 12 (approximate numbers).

One mallard banded in a previous year was recaptured in 1997 (2357-98802).

Traps: Number of birds caught and captured were probably not significantly different between trap types: x=65 ducks/trap for WW traps and 54 for PVC traps (3.7 and 2.6 ducks/trap-day for each type, respectively). WW traps were a bit more stable, made a better seal with the bottom and appeared to lose fewer ducks than the PVC traps, during herding to the exit hole (although the difference did not seem large). We placed a WW trap next to another (<1m away) that was doing extremely well and they both continued to capture large numbers of ducks (traps 6s and 7s, Table 1).

DISCUSSION

Thousands of ducks, primarily mallards, northern pintails and American green-wing teal, appeared to be using the LRS area for feeding and roosting. The banding effort was a success--many ducks were banded with an average number of mortalities and no major catastrophes. Setting up traps was relatively straight-forward with the WW and PVC traps and cannot recommend any major improvements with the system we used. While we banded more birds from the WW traps, and they were larger, we can’t claim a relationship between the trap size or type and trapping success (R. Oates did mention an experiment where the results showed an out come of larger traps catching more ducks). Besides not running the appropriate statistics on the numbers, total numbers of captured birds, including recaptures, were not recorded for each trap. In any case, the large WW traps had the largest catches and I would recommend future PVC traps to be built larger. If large numbers of ducks are captured, it invariably takes more than one time to get the ducks into the holding box, due to the crowding effect (it’s not that there is no more room in the box, ducks just resist going into a crowded box). Advantages of the 2 trap types were:

WW: Large size

More stable (PVCs were pretty wobbly, although this was not a real problem).

Are easier to press into the mud for a good seal with the substrate.

Ease of construction.

Didn’t stand out as much as the PVC traps.

PVC: Netting is easier on birds; probable reduced injury to bills, wings.

Light weight, though bulky.

Other suggestions would be to attach netting to the inside of WW traps to help protect bird wings and bills from injury. This must be done prior to set up in the field. PVC traps might be built out of a lighter-colored material. They really stand out (although they DO catch ducks).

We placed 2 WW traps together at the far end of the lake where ducks were dense. These were 2 of our best performing traps. It helped having them together because it cut down on travel time. Several traps in a dense duck area will produce more duck captures than more traps spread around in areas with fewer ducks; we eventually moved a PVC trap to this end of the marsh as well (although we kept it >100m from the others). We were concerned in placing traps so close because it is very disturbing to ducks when working an adjacent trap. We used 2 catch boxes for this operation and captured ducks simultaneously. We used a lower-impact panel trap for the last trap we placed ca.100m from the double trap because they did respond (flying up, etc.) to our banding operation 100m away.

Exposure and stress were probably the main cause of our mortalities--more died during a period of bad weather. We banded several birds that were slightly comatose but apparently recovered after warming them up for several minutes. Methods to reduce the mortality rate might include installing platforms where ducks can get out of the water (but cannot pin themselves beneath the platform). Probably best to them well above the water line, and at least a foot away from any trap wall; otherwise ducks might get caught up against and beneath them. Checking traps 2x/day might also spare birds (and placing fewer traps but in high density areas might allow for this).

Band numbers used in 1997 were:

7A (mallard): 235798-801 to -914; 235798-952 to -963; 235798925 and 75614570.

6 (pintail, widgeon, shovelers and scaup): 656-36201 to -36300, 656-36752 to -36800, 656- 39001 to -39068, 756-14501 to -14700, 756-14902 to -15000, 656-39024, 756-14910, 756-14881 and 756-14519.

5 (optional scaup, shoveler): 635-00101 to -00102.

4 (green-wing teal): 584-01984 to -01750, 654-09748 to -09800, 654-09830 to -09885.

Additional Recommendations

1. Move traps that go through extended periods of inactivity, especially following changes in water depth or other conditions; move traps that consistently produce very high percentages of recaptured ducks.

2. Check for stolen traps (2 panel traps) in vicinity of LRS.

3. Install wire door in last PVC panel trap.

4. Replace borrowed, fiberglass canoes with USFWS aluminum canoes.

ACKNOWLEDGMENTS

This report was prepared by Dennis Marks and Larry Barnes. To streamline preparation, the WP document for the 1996 report by Steve Lane was used and plagiarized. Thanks to Bill Sherwood and John Hendrickson for the annual use of their canoes; Bill Mans and the owners of the other nearby cabins who graciously allowed duck banders to use their facilities; USFWS Division of Law Enforcement for providing their cabin as our banding headquarters; Jim Clinton for letting us store all our "north-side" trapping equipment at his cabin.

REFERENCES

Platte, R.M. 1994. Pre-season Duck Banding - Lewis River Slough - Upper Cook Inlet, 1994.

Unpublished report. USFWS, Migratory Bird Management Project. Anchorage. 17 pp.

Balogh, G.R. 1993. Pre-season Duck banding in Upper Cook Inlet, 1993.

Internal memo. USFWS, Migratory Bird Project. Anchorage. 8pp.

Rosenberg, D.H. 1990. Alaska Department of Fish and Game 1990 Duck Banding

Report, Cook Inlet. ADF&G, Division of Wildlife Conservation. Anchorage. 8pp.

Rosenberg, D.H. 1991. Alaska Department of Fish and Game 1991 Duck Banding

Report, Cook Inlet. ADF&G, Division of Wildlife Conservation. Anchorage. 8pp.

Rosenberg, D.H. 1992. Alaska Department of Fish and Game 1992 Duck Banding

Report, Cook Inlet. ADF&G, Division of Wildlife Conservation. Anchorage. 8pp.

Rosenberg, D.H. 1993. Alaska Department of Fish and Game 1993 Duck Banding Report, Cook Inlet. ADF&G, Division of Wildlife Conservation. Anchorage. 8 pp.

Table 1. Total number of ducks captured and banded in 1997. By date and trap number. See Table 2 for species breakdown.

1 Trap Types: welded wire medicine hat (W) and PVC panel trap (P, see Methods).

Catch totals for each of the trap types were: W: 392 ducks in 112 trap days (3.7 ducks per trap day); P: 338 ducks in 129 trap days (2.6 ducks per trap day).

‘Trap 2' was moved to ‘trap 8' on 8 August.

Table 2. Total number of ducks captures and banded by species, sex and age class.

Table 3. Number of ducks banded for each year for the past 8 years.

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