USE OF PREDATOR EXCLOSURES TO PROTECT PIPING PLOVER NESTS IN ALBERTA AND SASKATCHEWAN Field Season Report. Lance Engley and Isabelle Michaud

Transcription

1 USE OF PREDATOR EXCLOSURES TO PROTECT PIPING PLOVER NESTS IN ALBERTA AND SASKATCHEWAN 2000 Field Season Report Lance Engley and Isabelle Michaud In cooperation with: Alberta Environment, Fisheries and Wildlife Management Division Alberta Sport, Recreation, Parks & Wildlife Foundation Canadian Wildlife Service North American Waterfowl Management Plan World Wildlife Fund

2 ACKNOWLEDGEMENTS Thank you to the agencies whose generous funding made this project possible: Alberta Conservation Association, Alberta Sport, Recreation, Parks & Wildlife Foundation, Alberta Environment, Fisheries and Wildlife Management Division, North American Waterfowl Management Plan, and World Wildlife Fund. Thank you to everyone (in alphabetical order) that contributed to the project through time in the field, sitting in meetings, building exclosures, sharing ideas or contributing data: Ron Bjorge, Steve Brechtel, Gordon Court, Paul Goossen, Ed Hofman, Dave Moore, Dave Prescott, Tom Sadler, and Gary Walsh. Finally, thank you to the field staff, Jeff Adamyk, Sherry Feser, Greg McClelland, Camila Morcos, Mark Piorecky, and Roy Schmelzeisen for all their hard work and long hours in the field. i

3 TABLE OF CONTENTS ACKNOWLEDGEMENTS... i INTRODUCTION... 1 STUDY AREA AND METHODS... 1 RESULTS... 3 DISCUSSION... 6 LITERATURE CITED... 8 APPENDIX 1. Maps of nesting sites on study lakes APPENDIX 2. Original data from 2000 field season LIST OF FIGURES Figure 1. Map of study area, Figure 2. Trend in the population of Piping Plovers on nine key breeding lakes in Alberta... 5 Figure 3. Location of Piping Plover nests on Birch Lake in Error! Bookmark not Figure 4. Location of Piping Plover nests on Cipher Lake in Error! Bookmark not Figure 5. Location of Piping Plover nests on Chain Lake #4 in Error! Bookmark not Figure 6. Location of Piping Plover nests on Freshwater Lake in Error! Bookmark not Figure 7. Location of Piping Plover nests on Sunken Lake in Error! Bookmark not Figure 8. Location of Piping Plover nests on Dowling Lake in Error! Bookmark not Figure 9. Location of Piping Plover nests on Killarney Lake in Error! Bookmark not Figure 10. Location of Piping Plover nests on Metiskow Lake in Error! Bookmark not Figure 11. Location of Piping Plover nests on Handhills Lake in Error! Bookmark not Figure 12. Location of Piping Plover nests on Piper Lake in Error! Bookmark not Figure 13. Location of Piping Plover nests on West Reflex Lake in Error! Bookmark not LIST OF TABLES ii

4 Table 1. Nest summaries for study lakes... 3 Table 2. Summary of banding in Table 3. Summary of 2000 adult and brood surveys... 4 Table 4. Number of adult Piping Plovers observed on selected Alberta lakes between 1986 and iii

5 INTRODUCTION The Piping Plover is designated as 'endangered' in Canada, 'threatened' in the U.S. (COSEWIC 2000, U.S. Fish and Wildlife Service 2000) and is listed as 'endangered' under the Alberta Wildlife Act. Nest predation has been identified as a significant limiting factor to Piping Plover reproductive success in the Great Plains (Whyte 1985, Haig 1992, Heckbert 1994, Richardson 1999). Results from studies carried out in east-central Alberta from 1995 to 1997 showed that through the use of predator exclosures, Piping Plover nest predation can be significantly reduced thus increasing productivity (Heckbert and Cantelon 1996, Richardson 1999). Consequently, a management project implementing the use of predator exclosures on a large-scale basis was initiated in Alberta in 1998 and is ongoing. STUDY AREA AND METHODS The predator exclosures used in the 2000 field season were circular in shape, made of a single length of stucco wire approximately 9 m long and 1.2 m high. The two ends of the stucco wire were attached with a 1.5 m length of re-bar, woven through the wire where it overlappped, creating an exclosure approximately 3 m in diameter. Four additional pieces of re-bar were attached to the exclosure at even intervals and inserted into the substrate for stabilization. In an effort to prevent birds from perching on the exclosures, the horizontal wire along the top of the exclosure was removed in order to expose the vertical wires. The bottom of each exclosure was secured in place by using 10 cm nails, bent at the top. To protect against aerial predators, the tops were covered with 2 cm x 2 cm plastic mesh, secured with 10 cm long cable ties. Smaller exclosures, used in previous field seasons (e.g., Michaud and Prescott 1999, Richardson 1999) were applied to nests on Birch Lake. These exclosures were square-pyramidal in shape, made of four stucco wire panels with bottom width of 1.2 m and top width of 60 cm. The four panels were attached together with hog clips. The exclosures were supported by four-1.5 m pieces of re-bar attached to each corner and driven into the ground for stabilization. The bottom of each exclosure was secured in place by inserting two-10 cm nails, bent at the top, into the ground on each of the four sides. Finally, to guard against aerial predators, the top was woven with bailing twine at 10 to 15 cm intervals. Beginning in early May, potential breeding lakes were surveyed for returning Piping Plovers. In order to maximize the efforts of the researchers, only lakes with easy access and relatively large Piping Plover populations were included in the management initiative. Twelve waterbodies were divided into three study areas based on geographic location. Lakes in the east-central part of the province (Figure 1) included: the westernmost of the Reflex Lakes (hereafter called Reflex Lake), Killarney Lake, Freshwater Lake, Cipher Lake, 'Piper Lake', Metiskow Lake and Sunken Lake. In the Hanna area surveyed lakes were: Little Fish Lake, Handhills Lake, Dowling Lake and 'Chain Lake #4'. Birch Lake near Vermilion was also included. Pair and brood surveys were carried out on all 12 lakes: Most of these lakes have been surveyed annually since 1989 and some since Pair surveys were carried out from 25 May to 7 June and brood surveys were carried out from 3 to 11 July. Lakes were surveyed on foot by walking approximately 60 to 70% of the way between the water and the vegetation line and stopping periodically to scan for plovers. Location of adults and juveniles were recorded and mapped. 1

6 Edmonton Red Deer Birch # Wainwright Cipher Reflex Killarney ## # # Metiskow # Sunken Freshwater # Piper Chain #4 # # Dowling # Handhills Drumheller # Little Fish Oyen Calgary Brooks Lethbridge Medicine Hat Kilometers Figure 1. Map of study area,

7 Census, exclosure application, and monitoring techniques followed the procedures outlined by Richardson (1997). For nests that had exclosures applied, they were erected within one day of discovery, regardless of the stage of incubation. Two researchers carried the exclosure to the nest and secured it to the substrate with the five re-bars and the bent nails. After application, each nest was monitored from 70 to 100 m away until the adults resumed incubation. Enclosed nests were monitored every second or third day throughout the incubation period. Changes in nest status were noted including predation of eggs, predation of adult(s), unexplained abandonments and hatching. Traditional nest success was calculated by dividing the number of successful nests (those hatching at least one chick) by the total number of nests for each lake. RESULTS A total of 58 nests were found on 11 waterbodies (Table 1). Overall hatching success (those nests hatching at least one egg) was 60% (35/58). Nests that were treated with exclosures for either part or all of the incubation period hatched 22 of 35 nests (63%). The twenty-three nests treated with large predator exclosures for the entire incubation period had 48% (11/23) hatching success. Of the 12 nests where large exclosures were applied and then removed during incubation, 92% (11/12) were successful. For nests where exclosures were not applied at all, 53% (10/19) were successful. On Birch lake, where small predator exclosures were applied, 75% (3/4) of the nests hatched. Adult plovers were confirmed depredated at 6% (2/35) of large exclosures, one each on Reflex and Killarney Lakes. Evidence of adult kills was found directly outside of the exclosures. Remains of plovers were seen as several contour feathers on Killarney Lake and a partial carcass, including head and feathers, on Reflex Lake. No adult plovers were killed at the small exclosures on Birch Lake. Table 1. Nest summaries for study lakes Lake Name Province No. of Nests No. Successful Nests Traditional Nest Success Birch Lake AB Chain Lake #4 AB Cipher Lake AB Dowling Lake AB Freshwater Lake SK Handhills Lake AB Killarney Lake AB Metiskow Lake AB Piper Lake AB Reflex Lake AB/SK Sunken Lake AB Total: The fates of the 35 nests originally treated with large predator exclosures is as follows: 11 nests hatched with the exclosures left on until the end of incubation. 1 nest was depredated inside of the exclosure 9 nests were abandoned for unknown reasons, possibly adult predation 2 nests failed because adults were depredated 11 nests hatched after the exclosures had been removed 1 nest was depredated after the exclosure had been removed 3

8 Sixty-three chicks were banded in Bands were placed in combinations identifying year and lake of origin (Table 2). In addition to observations of newly banded chicks, 14 re-sightings of birds banded in either Alberta, Saskatchewan, or on the wintering grounds, were recorded. Table 2. Summary of banding in 2000 Lake Band Combination 1 No. of birds banded Baxter 2 -, Y : -, B/W m 11 Birch -, G m: -, B/W 6 Freshwater -, B/W : -, W m 7 Metiskow -, B/W O : -, m 4 Reflex -, O m : -, B/W 33 Sunken -, B/W m : -, B/W 2 Total: 63 1 Leg band combinations read as follows: upper left, lower left: upper right, lower right. Dashes (-) mean no bands were located on that part of the leg. The lowercase letter m refers to a metal band, uppercase letters refer to the colours of plastic bands, and letters separated by a slash (/) are striped bands. Consecutive letters mean bands were stacked where the first letter refers to the colour of the band highest on the leg. 2 Not included in predator exclosure study. Adult and brood surveys were carried out on 12 waterbodies (Table 3). No significant population changes were recorded as numbers of Piping Plovers on lakes are within the levels measured since the beginning of the survey (Table 4). However, the trend in the Piping Plover population since 1994 on nine key breeding lakes in the province appears to be downward (Figure 2). Table 3. Summary of 2000 adult and brood surveys Adult Survey Brood Survey Observer Lake # Adults # Adults #Young Birch I. Michaud & S. Feser Chain Lake # M. Piorecky & R. Schmelzeisen Dowling M. Piorecky & R. Schmelzeisen Handhills M. Piorecky & R. Schmelzeisen Killarney L. Engley & C. Morcos Little Fish M. Piorecky & R. Schmelzeisen Reflex L. Engley & C. Morcos Freshwater L. Engley & C. Morcos Piper L. Engley & C. Morcos Sunken L. Engley & C. Morcos Cipher L. Engley & C. Morcos Metiskow L. Engley & C. Morcos Total

9 Table 4. Number of adult Piping Plovers observed on selected Alberta lakes between 1986 and 2000 a. When repeat surveys were conducted in the same year, maximum numbers recorded are given (after Prescott 1997, Richardson 1999). LAKE YEAR 'Chain #4' Chappice b Dowling Handhills Killarney Little Fish 'Rider' Rockeling Bay Reflex a sources: Bjorge (1996), Goossen (1991, 1994, unpubl. data), Heckbert (1994), Heckbert and Cantelon (1996), Hofman (1990, 1991, 1992, 1993, 1994 and unpubl. data), Lord (1989), Richardson (1998), Wershler (1988, 1992), Wershler and Wallis (1987), Michaud and Prescott (1999). b partial survey Count Year Figure 2. Trend in the population of Piping Plovers on nine key breeding lakes in Alberta (see Table 4), Years where surveys were largely incomplete were omitted from the analysis. 5

10 DISCUSSION Between , adult kills were recorded at 0-7.5% of exclosures (range 0-3) compared to 33.8% (23/68) of exclosures in In an attempt to reduce adult predation, larger predator exclosures were utilized in Adult predation at exclosures has been observed in other areas of the Great Plains (B. Murphy, pers. comm.). Preliminary results in some areas show that adult losses are much lower at large (>3 m diameter) exclosures (B. Murphy, pers. comm.). In May 2000, the Alberta Piping Plover Ad Hoc Committee decided that the large exclosures would be removed from the nests on a given lake once the number of adults depredated at exclosures totalled three. On 12 June 2000 an adult Piping Plover was confirmed killed at an exclosure on Reflex Lake. Two other nests in the immediate vicinity (~ 25 and 45m away) were also found abandoned on the same day. Broken eggs in the nest bowl, resulting from a hailstorm, was evidence of the abandonment. Although it is possible that the nests were abandoned as a direct result of the hailstorm, this is unlikely, as the remaining 15 nest that were active on the rest of Reflex Lake remained active after the storm. Merlins are thought to be the primary cause of adult depredation at exclosures (Michaud and Prescott 1999). It is typical of Merlins to return to the immediate vicinity of a successful kill, until the food supply in that area has been exhausted (G. Court, pers. comm.). It is therefore believed that the two nests in the area immediately surrounding the one with the depredated adult, were not abandoned, but also failed as a direct result of adult depredation. With these three nests believed to have failed due to nest predation, it was decided that each of the exclosures on Reflex Lake would be removed. All seven of the nests from which exclosures were removed hatched within six days of removal. The majority of incubation was completed with the protection of the exclosure. Another adult was subsequently confirmed killed on 16 June 2000 on Killarney Lake. With this discovery a decision was made to remove exclosures from the five remaining active nests on all of the lakes. Four of these five nests subsequently hatched. In previous years, cattle damage to the exclosures has been a problem. Five nests were abandoned in 1999 as a direct result of cattle damage (Michaud and Prescott 1999). In 2000, cattle damaged only one exclosure, and this nest still hatched all four eggs. The larger exclosures provided a bigger buffer zone between the cattle and the nest. This may be the reason that the one exclosure that was damaged by cattle did not result in an abandoned nest. 6

11 Nest predation is still a limiting factor; therefore research on this management technique must continue in order to maximize increases in productivity. Nest predation, as well as other management issues that should be addressed include: 1. Other alternative exclosure designs should be studied as to their effects on cattle damage and adult depredation. For instance, exclosures smaller than the present design, without tall rigid sides, may be less attractive to both raptors and cattle. 2. Efforts should continue to minimize damage to exclosures in areas where nesting beaches are accessed by livestock. It is likely that the size and mere presence of exclosures on beaches entices cattle to use the structures as scratching posts. Restricting cattle from nesting areas during the nesting period (i.e., May to July) would eliminate this as well and lessen degradation of soft nesting substrate by deep footprints. 3. Banding Piping Plover chicks should continue as recoveries and sightings of banded birds are important to increase the knowledge base for the species. The International Piping Plover Census planned in the year 2001 will provide increased opportunity for observations of banded birds across the Piping Plover s winter and summer range. 4. A broad scoped Piping Plover management strategy needs to be developed for Alberta. Combinations of limiting factors and management issues are often specific to individual nesting areas making it difficult to apply a general management strategy for the entire Piping Plover population. For instance, any management strategy should include ways of addressing habitat protection, reduction of nest and chick predation, control of vegetation encroachment and mitigation of human disturbance factors. 7

12 LITERATURE CITED Bjorge, R. R The 1996 Piping Plover census in Alberta, executive summary. Unpubl. rept., Alberta Natural Resources Service, Parkland Region, Red Deer, AB. 7 pp. COSEWIC Canadian species at risk. Committee on the Status of Endangered Wildlife in Canada. URL: (revision date: 30 Nov 2000). Goossen, J. P Prairie Piping Plover conservation: third annual report (1990). Unpubl. rept., Canadian Wildlife Service, Edmonton, AB. 28 pp. Goossen, J. P Prairie Piping Plover conservation: 1992 and Unpubl. draft rept., Canadian Wildlife Service, Edmonton, AB. 34 pp. Haig, S. M Piping Plover (Charadrius melodus). In The Birds of North America, No.2 (A. Poole, P. Stettenheim and F. Gill, eds.). Academy of Natural Sciences, Philadelphia, PA. 18 pp. Heckbert, M. D Piping Plover (Charadrius melodus) ecology and conservation in Alberta (1994): Reflex Lake and Killarney Lake field report. Unpubl. rept. for Alberta Fish and Wildlife Service, Northeast Region, Vermilion, AB. 152 pp. Heckbert, M. D. and K. D, Cantelon Piping Plover (Charadrius melodus) ecology and conservation in Alberta (1995): east-central Alberta field report. Unpubl. rept. for Alberta Fish and Wildlife Service, Northeast Region, Vermilion, AB. 163 pp. Hofman, D. E Piping Plover survey, Little Fish Lake, Alberta. Unpubl. rept., Alberta Fish and Wildlife Division, Red Deer, AB. 22 pp. Hofman, D. E Piping Plover survey, Little Fish Lake, Alberta. Unpubl. rept., Alberta Fish and Wildlife Division, Red Deer, AB. 18 pp. Hofman, D. E Piping Plover survey, Little Fish Lake, Alberta. Unpubl. rept., Alberta Fish and Wildlife Division, Red Deer, AB. 16 pp. Hofman, D. E Piping Plover survey, Little Fish Lake, Alberta. Unpubl. rept., Alberta Fish and Wildlife Division, Red Deer, AB. 8 pp. Hofman, D. E The 1991 Piping Plover census in Alberta. Pp in The 1991 international Piping Plover census in Canada (S. P. Flemming, ed.). Can. Wildl. Serv. Occ. Pap. No pp. Lord, S Piping Plover surveys at Little Fish Lake. Unpubl. rept., Canadian Wildlife Service, Edmonton, AB. 10 pp. 8

13 Michaud, I., and D. Prescott Use of predator exclosures to protect Piping Plover nests in Alberta and Saskatchewan. Unpubl. rept., Alberta Conservation Association, Edmonton, AB. 20pp. Murphy, R. K., K. A. Smith, B. Anderson, and M. L. French. In preparation. Raptors kill Piping Plovers tending nests within predator exclosures in North Dakota. Prescott, D. R. C Status of the Piping Plover (Charadrius melodus) in Alberta. Alberta Environmental Protection, Wildlife Management Division, Wildlife Status Report No. 1, Edmonton, AB. 19 pp. Richardson, I. M Guidelines for the use of predator exclosures to protect Piping Plover (Charadrius melodus) nests. Alberta Environmental Protection, Wildlife Management Division Report, Edmonton, AB. 21 pp. Richardson, I. M Use of predator exclosures to protect Piping Plover nests in Alberta and Saskatchewan. Unpubl. rept., Alberta Conservation Association, Edmonton, AB. 20pp. Richardson, I. M Predator exclosures: a management technique to increase Piping Plover reproductive success in the Canadian Prairies. M. Sc. Thesis, University of Alberta, Edmonton, AB. 65 pp. U. S. Fish and Wildlife Service Division of Endangered Species. U. S. Fish and Wildlife Service. URL: (revision date: 12 Dec 2000). Wershler, C. R Piping Plover studies Alberta Unpubl. rept. for Alberta Recreation and Parks, World Wildlife Fund Canada, Alberta Fish and Wildlife, and Canadian Wildlife Service, Calgary, AB. 33 pp. Wershler, C. R An analysis of Piping Plover management concerns in Alberta. Unpubl. rept. for Alberta NAWMP Centre, Edmonton, AB. 56 pp. Wershler, C. R., and C. Wallis Status of the Piping Plover in Alberta, Unpubl. rept. for World Wildlife Fund Canada and Canadian Wildlife Service, Calgary, AB. 54 pp. Whyte, A. J Breeding ecology of the Piping Plover (Charadrius melodus) in central Saskatchewan. M. Sc. thesis, Univ. Saskatchewan, Saskatoon, SK. 153 pp. 9

14 APPENDIX 1. Maps of nesting sites on study lakes. Note: The following maps are meant to give general locations of nests on nesting lakes and are not to scale. Georeferenced information can be accessed through the Biodiversity Species Observation Database (BSOD) maintained by the Alberta Conservation Association and Alberta Environment. 10

15 APPENDIX 2. Original data from 2000 field season. Nest No. (1) Treated=1 Eggs Laid Eggs Hatched Comments BILA successful, 1 young dead in nest bowl BILA successful BILA successful BILA did not hatch after full incubation period eggs sterile CHL nest depredation CHL successful CILA nest hatched after removal of exclosure DOLA nest failure caused by cattle DOLA nest failure caused by cattle DOLA nest depredation DOLA successful DOLA nest depredation FRLA unexplained abandonment FRLA successful FRLA unexplained abandonment FRLA nest hatched after removal of exclosure FRLA nest hatched after removal of exclosure FRLA unexplained abandonment FRLA successful HALA unexplained abandonment HALA unexplained abandonment HALA unexplained abandonment HALA unexplained abandonment KILA successful KILA successful KILA nest failure directly a result of adult depredation KILA nest depredated after removal of exclosure KILA nest hatched after removal of exclosure MELA successful PILA nest depredation PILA nest depredation PILA unexplained abandonment RELA nest depredated inside exclosure RELA successful RELA successful RELA successful RELA successful RELA successful RELA successful RELA successful RELA unexplained abandonment RELA nest hatched after removal of exclosure RELA nest failure directly a result of adult depredation RELA unexplained abandonment RELA nest hatched after removal of exclosure RELA nest hatched after removal of exclosure RELA successful 11

16 RELA nest hatched after removal of exclosure RELA nest hatched after removal of exclosure RELA nest hatched after removal of exclosure RELA nest hatched after removal of exclosure RELA successful RELA successful RELA successful RELA nest depredated SULA successful SULA nest depredated SULA successful (1) Lake codes: BILA- Birch, CILA- Cipher, CHL4- Chain Lake #4, DOLA- Dowling Lake, FRLA- Freshwater, HALA- Handhills, KILA- Killarney Lake, MELA- Metiskow Lake, PILA- Piper Lake, RELA- Reflex, SULA- Sunken Lake 12