LEAST TERN AND PIPING PLOVER NEST MONITORING FINAL REPORT 2012

Transcription

1 The Central Nebraska Public Power and Irrigation District Holdrege, Nebraska LEAST TERN AND PIPING PLOVER NEST MONITORING FINAL REPORT 2012 NOVEMBER, 2012 Mark M. Peyton and Gabriel T. Wilson,

2 Page 1: This report is submitted in accordance with conditions of U.S. Fish and Wildlife Service permit number TE , Nebraska Game and Parks Commission 2012 Scientific Collecting Master Permit, and Article 423 of the Federal Energy Regulatory Commission License for Project No issued on 29 July The purpose of the project was to identify and monitor nest sites of least terns (Sternula antillarum) and piping plovers (Charadrius melodus) in the upper Platte River Valley (Lexington to North Platte), South Platte River Valley (Brule to Sutherland), North Platte River Valley (Oshkosh to Lewellen) and along the shore of Lake McConaughy. Following the summary, Section 1 reviews the results from the North Platte River, South Platte River, and Lake McConaughy. Section 2 reviews the results from the upper Platte River and associated sandpits, and Section 3 presents a cumulative review of the past 21 seasons, SUMMARY Since 1992 The Central Nebraska Public Power and Irrigation District (Central), under permits from the U.S. Fish and Wildlife Service and the Nebraska Game and Parks Commission, has been surveying for, and managing nesting areas of, the federally endangered least tern (Sternula antillarum) and the threatened piping plover (Charadrius melodus) along the shore of Lake McConaughy and stretches of the North Platte, South Platte, and upper Platte rivers. Starting in 2003 Central included snowy plovers (C. alexandrinus) nesting at Lake McConaughy in its monitoring efforts. During 2012, Central personnel surveyed the shore of Lake McConaughy, the upper Platte River Valley and associated sandpits from Lexington to North Platte, the North Platte River and associated sandpits from Oshkosh to Lewellen, and the South Platte River and associated sandpits from Big Springs to Sutherland. Nest sites of piping plovers and/or least terns were identified and monitored at least twice weekly throughout the nesting season at the sandpits along the Platte River, and daily on the shore of Lake McConaughy. Warning, No Vehicles Beyond This Point, Keep Out, and Stay Back 50 Feet signs and red twine psychological fencing were used to identify nest areas in an effort to prevent destruction of the nests by human activities. Along the shore of Lake McConaughy five pairs of least terns produced five nests with 10 eggs. Three nests successfully hatched four chicks, of which all four reached fledge stage (defined as a chick a minimum of 21 days old, or observed flying) for a ratio of 0.80 fledglings/adult pair and 0.80 fledglings/nest. Forty-three pairs of piping plovers produced 67 nests along the shore of Lake McConaughy with 43 successfully hatching at least one chick. From the 222 known eggs, 159 chicks hatched with 93 of those successfully reaching fledging age (defined as a chick a minimum of 24 days old, or observed flying) for a fledge ratio of 1.98fledglings/adult pair and 1.38 fledglings /nest.

3 Page 2: At the three locations in the upper South Platte and Platte River Valley monitored by Central, 20 pair of least terns produced 10 nests, which hatched 14 chicks, seven of which reached flight capability. This resulted in a minimum fledge ratio of 0.70 fledglings/adult pair. Nine pair of piping plovers initiated nine nests producing 26 chicks with 14 reaching fledging age for a ratio of 0.78 fledglings/adult pair and 1.56 fledglings/nest. Over the past 21 years Central personnel have documented 478 pair of least terns initiating 531 nests which hatched 667 chicks, with a minimum of 417 (62.5%) successfully reaching flight capability for a fledge ratio of 0.87 fledglings/adult pair or 0.79 fledglings/nest. During that same time period, 1,883 pair of piping plovers hatched 4,113 chicks from 2,343 nests with a minimum of 2,544 (61.9%) reaching flight capability for a fledge ratio of 1.35 fledglings/adult pair or 1.09 fledglings/nest. SECTION 1 LAKE McCONAUGHY Because there are approximately 75 miles of shoreline at Lake McConaughy (at full pool), the shoreline is normally broken into 12 regions (see Appendix A). Piping plover nested in seven of these regions (B, D, E, F, G, I, and J). Least tern nests were located in two regions, B and F. SURVEYS: Nests were located by walking and driving slowly along the beach starting in mid-to-late April. Once located, nests were protected by diamond-shaped enclosures approximately 250 square meters in size. The enclosures consisted of four posts with orange twine and tape acting as a psychological" fence. KEEP OUT, ATTENTION, and STAY BACK 50 FEET signs were placed on the posts. Once located, nest location was determined with a GPS unit, a 3 x3 x4 wire enclosure was placed around plover nests and anchored with steel posts, and the nest was monitored on a daily basis until the fate of the nests and chicks could be determined. MANAGEMENT: Two larger areas were fenced using bright orange snow fence with KEEP OUT signs, one area had the signs with no fence, and two areas were signed with NO VEHICLES BEYOND THIS POINT. The fenced areas were the Swimming Beach parking lot and the large enclosure in Little Thunder Bay that is excluded every year. On the beach below the parking lot approximately 200 meters of beach were set aside from vehicles and then an additional 300 meters were signed with KEEP OUT signs. The final area was a NO VEHICLES area at Sand Point.

4 Page 3: PUBLIC EDUCATION: Informational signs and boxes with free literature were placed at a variety of locations around the lake. Central also placed information concerning piping plovers and least terns on its internet website ( ). LEAST TERNS (Sternula antillarum): Ten least tern adults (five pair) were observed in association with five nests. The five nests produced four chicks, all of which were documented as reaching fledging age for a minimum ratio of 0.80 fledglings/adult pair and 0.80 fledglings/nest. PIPING PLOVER (Charadrius melodus): Forty-three pairs of piping plovers initiated 67 nests, hatching 159 chicks of which 93 were observed to reach fledge stage for a fledge ratio of 1.98 fledglings /adult pair and 1.38 fledglings/nest (see Table 1). NEST LOSSES: Nineteen piping plover and two least tern nests were lost prior to, or at the time of, hatching. The cause of plover nest lost was predation (nine), weather (eight), and two nests were abandoned. Tern nest loss was undetermined Plover nests that were lost, on average, survived 13 days with one observed for 32 days prior to being lost. The Mayfield estimate of daily survival for piping plovers was which results in an estimated 75.5% hatch success compared to an apparent hatch success of 69%.

5 Page 4: Table 1. Lake McConaughy Piping Plover Nesting Results 2012 Area Location Nests Chicks Fledged Fledged/Nest Ratio A West End North B Otter Creek C Sand Point ,00 D Lemoyne West E Lemoyne East F Little Thunder Bay G Martin Bay H K-1 Region I Kildare Bay J Van's East K Van's West L West End South Totals

6 Page 5: SECTION 2 UPPER PLATTE RIVER VALLEY Central personnel surveyed four sites in the upper Platte River Valley between Lexington and North Platte and the South Platte Valley between North Platte and Hershey. Both least terns and piping plovers were found nesting at three of the locations. One area in the Platte Valley is owned by Central. This area is the sand and gravel dredge pile at Central s Diversion Dam near North Platte, Lincoln County, Nebraska (UTM coordinates x = , y = ). The other location is owned by Paulson's Inc. and is a sandpit spoil pile in Dawson County (Koch's South at Cozad, UTM coordinates x = , y = ). Neither terns nor plovers were seen at Kirkpatrick's Sandpit near Gothenburg, Dawson County, Nebraska (UTM coordinates x = , y = In addition, the sandpit located south of Interstate 80, west of North Platte in the South Platte Valley was surveyed again and both least terns and piping plovers were located. This pit is also owned by Paulson s Inc. and is a sandpit spoil pile located in Lincoln County, Nebraska (UTM coordinates x = , y = ). Three bank line or point-bar nesting habitat areas, approximately 40 acres each, were created along Central s Jeffrey Island Habitat Area, located in Dawson County between Lexington and Overton, Nebraska, in 2002, 2004, and 2007Least terns have been observed on multiple occasions foraging near all three areas; however, no least terns or piping plover nests were located. Weekly surveys were conducted from 22 April through 27 July to identify active nesting areas. Nests at all locations were located using binoculars and spotting scopes. Keep Out and Attention signs were placed around areas where least terns and/or piping plovers constructed nests. The nests at the areas managed by Central were monitored twice weekly. MANAGEMENT: Following multiple years of herbicide treatment, no herbicide was utilized in No human-related problems were recorded at these locations. LEAST TERNS (Sternula antillarum): Least terns were found nesting at three of the four locations monitored during Ten pair of least terns constructed 10 nests that hatched a minimum of 14 chicks of which seven fledged. This is a fledge ratio of 0.7 fledglings/adult pair and 0.7 fledglings/nest. A summary of least tern data from the upper Platte River Valley is given in Table 2.

7 Page 6: Table 2: 2012 Least Tern Nesting Data for the Upper Platte River Valley Location Koch's South Kirkpatrick's Diversion Dam Paulson's North Platte Totals Adults Nests Chicks Fledged Fledge Ratio PIPING PLOVERS (Charadrius melodus): Piping plovers nested at three of the four sites monitored during Nine pair of piping plovers constructed nine nests; seven successfully hatched 26 chicks with 14 reaching fledging age for a ratio of 1.56 fledged chicks/adult pair. A summary of the piping plover data from the upper Platte River Valley is given in Table 3. Table 3: 2012 Piping Plover Nesting Data for the Upper Platte River Valley Location Koch's South Kirkpatrick's Diversion Dam Paulson's North Platte Totals Adults Nests Chicks Fledglings Fledge Ratio

8 Page 7: SECTION 3 CUMULATIVE RESULTS The Central Nebraska Public Power and Irrigation District has been collecting data on the nesting success of least terns and piping plovers in the upper Platte River Valley and along the shore of Lake McConaughy for the past 21 seasons. Over that time period, Central personnel have documented 478 pair of least terns initiating 531 nests which hatched 667 chicks, with a minimum of 417 (62.5%) successfully reaching flight capability for a fledge ratio of 0.87 fledglings/adult pair or 0.79 fledglings/nest. During that same time period 1,883 pair of piping plovers hatched 4,113 chicks from 2,342 nests with a minimum of 2,544 (62.2%) reaching flight capability for a fledge ratio of 1.33 fledglings /adult pair or 1.09 fledglings /nest. Appendix C provides the cumulative results for each of the nesting areas monitored by Central for the years Thompson (1982), Prindville-Gaines and Ryan (1988) and Ryan et all (1993) calculated a minimum fledged per breeding pair ratio necessary to maintain a stable breeding population in least terns of 0.7 fledglings/adult pair and 1.13 fledglings /adult pair for piping plovers. At the time, these were the only calculated minimums necessary to provide for a stable population and as such they were adopted as our management goals for each species. At Lake McConaughy and the sites managed by Central on the Platte River, the reproductive successes of both least terns and piping plovers have exceeded these management goals over the 21 years as a whole. At Lake McConaughy, reproductive success has met or exceeded the management goals for least terns in 16 of the 21 years and for piping plovers 11 of 21 years. At Koch s South Pit the reproductive success has met or exceeded the goals 10 of the 21 years for least terns and 11 of the 21 years for piping plovers. At the Central s Diversion Dam the reproductive success of least terns met and/or exceeded the management goals 13 of the 21 years, but in only four years were the goals met for piping plovers. Loss of nests prior to hatching has, historically, been the single most limiting factor for piping plovers along the shore of Lake McConaughy. During the past 21 years 856 nests, or 36.5% of the total, have been lost prior to hatching. Once hatched, however, a majority of the chicks successfully reach fledging age. Over the past 21 years 4,113 chicks were verified as hatching with 61.8% fledged.

9 Page 8: Piping plover fledging Success at Lake McConaughy for the years is shown in Figure #1. Note: Fledge Success is defined as the number of chicks that successfully fledged divided by the total number of chicks observed Central personnel attempted to document the cause of both piping plover and least tern nest loss with the hope that by knowing the causes we could modify future management techniques that would limit or prevent these losses. In 2009, extensive and expanded monitoring showed that predators and specifically canine predation were by far the largest cause of nest loss. In 2010, Central utilized protective nest cages to reduce canine predation, however, rising lake levels resulted in extensive nest loss and the effectiveness of the cages was impossible to determine. During 2011, the limited amount of available habitat resulted in the lowest number of nests initiated in over 20 years and so again, the effectiveness of the cages was in question. In 2012, we once again had extensive beach and 62 nests were located prior to hatching. While effective in preventing canine predation, the cages actually seemed to attract attention from birds, primarily common grackles and 14 nests were impacted with half losing all eggs prior to hatching Monitoring and Management Plans Central is continuing to work with individuals from the U.S. Fish and Wildlife Service and the Nebraska Game and Parks Commission on management actions that will increase nest success and help provide protection for the young chicks after hatching. Central personnel met with individuals from both agencies on four separate occasions during Central has committed to hiring more help for monitoring in In addition, Central is talking with the U.S. Geological Survey on having technicians band plover chicks and then help in the

10 Page 9: monitoring activity. Also, in addition, the Nebraska Game and Parks Commission will provide technicians and supplies to aid in various management actions that as of this writing still have not be finalized. In 2013 Lake McConaughy is not expected to be at full pool on May 1 st. At present, we anticipate the lake will be at approximately the same elevation experienced in May During the first two weeks of that month the width of the beach from the waterline to the beach edge where nests were found averaged 176 feet. Thus we expect the same availability of habitat as was present in Central will continue to identify and fence individual nests established along the beach. In addition Central will again set aside larger areas in Martin Bay, Little Thunder Bay, Sand Point, and on the south side. To help protect the nests from predation Central will install a cage over each piping plover nest located in areas near high human use and/or non-forested areas. In isolated and forested areas where the threat from common grackles is greater than canines, no cage will be utilized. In addition, unless in a high use area, Central will not fence individual nests until there are 3 4 eggs in the nest. We believe this will limit abandonment of the nest by adults who will have much greater resources invested than a one or two-egg nest. Central will continue its extensive public education program of free literature and large informational signs as well as media spots on local and Denver television stations concerning the two species and will make information available on Central's internet website. Based upon the data gathered over 21 years at multiple sites in the upper Platte River and South Platte River Valleys and along the 75 miles of shoreline at Lake McConaughy, it is evident that these areas can be very productive and valuable as habitat for these two species. It is also evident that the habitat for both species is ephemeral and that during some years it will not be sufficient to meet the reproductive success levels as identified in Central s management plan. However, even during those less than optimum years we believe that Central s management actions have helped to protect the limited number of nests present, and as such those actions have had a positive impact on the protection and recovery of both species. Central will continue to consult with the U.S. Fish and Wildlife Service and the Nebraska Game and Parks Commission on various strategies to protect reproductive output for piping plovers and least terns at Lake McConaughy and other sites managed by Central.

11 References Peyton, Mark M A method for moving piping plover nests on reservoir shorelines. Proceedings of the Platte River Basin Ecosystem Symposium. pp Plissner, J. H., and S.M. Haig Viability of piping plovers (Charadrius melodus) metapopulations. Biol. Conserv. 92(2): Ryan Mark R., Brian G. Root, and Paul M. Mayer. Status of piping plovers in the Great Plains of North America: A demographic simulation model. Conservation Biology Volume 7, No. 3, Sept. 1993: Prindiville-Gaines, E. M., and M. R. Ryan Piping plover habitat use and reproductive success in North Dakota. Journal of wildlife Management 52:

12 APPENDIX A LEAST TERN AND PIPING PLOVER NESTING REGIONS AT LAKE McCONAUGHY

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14 APPENDIX B PIPING PLOVER NESTS ESTABLISHED AND LOST AT LAKE McCONAUGHY 2012

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16 APPENDIX C FLEDGING RATIOS FOR LEAST TERNS AND PIPING PLOVERS IN AREAS MONITORED BY CENTRAL NEBRASKA PUBLIC POWER AND IRRIGATION DISTRICT

17 Fledge Ratios for Least Terns (Sternula antillarum) and Piping Plovers (Charadrius melodus) in areas monitored by Central Nebraska Public Power and Irrigation District, LEAST TERNS PIPING PLOVERS Site Year Adult Pair Nests Fledge Ratio Adult Pair Nests Fledge Ratio McConaughy Subtotal

18 Koch's So. Cozad Subtotal

19 LEAST TERNS Adult pair Nests Fledge ratio PIPING PLOVERS Adult pair Nests Fledge ratio Central Diversion North Platte Subtotal Kirkpatrick's Gothenburg Subtotal

20 PIPING LEAST TERNS PLOVERS Adult Adult pair Nests Fledge ratio pair Nests Fledge ratio Lemmon Willow Isl. Pit Subtotal Potter's Pond Gothenburg Ogallala Ready Mix Subtotal Paulsen's Pit Ogallala Roscoe Sand Pit Subtotal Whitney Sand & Gravel, Sutherland Subtotal North Platte Paulson's West Subtotal TOTALS