Western Snowy Plover Breeding Summary for 2019

October 07, 2019 Posted by: Matt Lau

The goals of our 2019 western snowy plover efforts were to protect nesting pairs of plovers and to determine plover abundance, distribution, and breeding success at beaches within Point Reyes National Seashore (PRNS).

In 2019, we conducted 176 total surveys on park beaches to determine abundance and distribution of breeding snowy plovers: thirty-six (36) surveys from the Kehoe trail to Abbotts Lagoon; fifty-three (53) surveys from Abbotts Lagoon to North Beach parking lot; twelve (12) in the 2011 Dune Restoration Area; thirty-three (33) between North Beach parking lot and South Beach parking lot; five (5) from South Beach parking lot to Lighthouse Beach; thirty-four (34) on Limantour Spit; and three (3) on Drakes Spit.

A minimum estimate of twenty-three plovers bred at Point Reyes, a 39% decrease in population size compared to 2018 (n = 38 birds). Exclosures were placed around elevent of the thirty-five nests located in 2019. Of the thirty-five nests, twelve hatched at least one egg, and thirty-three of eighty-three eggs hatched. Hatch success for exclosed nests was 90.9% (ten of the eleven exclosed nests), compared to 8.3% for unexclosed nests (two of the twenty-two unexclosed nests). We observed a record number of nests lost due to common raven (Corvus corax) depredation (sixteen out of twenty-two nests that had failed).

Fifteen of thirty-three chicks survived for at least twenty-eight days after hatching, for a 45.5% fledging rate. The average fledging success rate in the previous five years was 35.8%. Per capita reproductive success (0.87) was slightly higher than in 2018 (0.70), but still below the 1.0 threshold that is needed to increase the population size (ignoring immigration and emigration into and out of the local population).

This season, with a total of thirty-five nests, had the lowest number of nests in the last six years, which is reflective of the population decline. Nesting at Limantour Beach declined after four consecutive years of increased breeding activity: there were six nests in 2019 and fifteen nests in 2018.

Furthermore, nesting activity in the 2011 Dune Restoration Area continued declining, to a low of three nests during the first months of the breeding season; no plovers were detected after May 1.

There was a significant increase in nesting activity on North Beach (NB), south of NB parking lot (five nests). We detected the first sign of breeding activity on South Beach this season, the first detection since the 1980s (this nest fledged at least one chick). On Kehoe Beach, we observed an unusual case of brood adoption by one adult male, who raised two of his own biological hatchlings to fledge, as well as an additional two biologically-unrelated hatchlings from another nest.

In partnership with Point Blue Conservation Science, the plover banding program continued at Point Reyes for a fifth year in 2019. Chicks were banded with aqua over violet on the left and brood combinations on the right. Thirty out of thirty-three total hatched chicks were banded. Fourteen of the thirty chicks banded survived to fledge. At least six of fourteen fledglings (42.8%) from the 2018 breeding season were observed in the park during surveys between March and September 2018. Only one of these fledglings was a confirmed breeder in 2019, indicating that many others bred outside of their natal area.

Disclaimer: These data are preliminary summary statistics from the 2019 breeding season and are subject to change.

Table 1. Number of western snowy plovers nesting at PRNS from 2010 to 2019.
Year Females Males Total
2010 6 8 14
2011 5 9 14
2012 4 5 9
2013 9 9 18
2014 13 16 29
2015 16 22 38
2016 17 22 39
2017 19 21 40
2018 18 20 38
2019 10 13 23
Table 2. Number of western snowy plover nests at PRNS by survey sector from 2010 to 2019.
Year Kehoe (K) Abbotts Lagoon to North Beach parking lot (NP) Abbotts Lagoon Restoration Area (RA) North Beach (NB) South Beach (SB) Limantour (L) Total
2010 7 8 NA 0 0 0 15
2011 3 12 NA 0 0 0 15
2012 2 4 1 0 0 0 7
2013 6 13 2 0 0 0 21
2014 6 25 14 0 0 0 45
2015 8 22 16 1 0 2 49
2016 7 26 6 0 0 3 42
2017 5 22 7 1 0 11 46
2018 5 20 7 3 0 15 50
2019 7 13 3 5 1 6 35
Table 3. Western snowy plover nest success on Point Reyes Beach from 2010 to 2019.
Year Number of Nests % of Nests with Eggs that Hatched Number of Eggs Number of Eggs Hatched % of Eggs Hatched Number of Chicks Fledged % of Chicks Fledged Chicks Fledged per Egg Laid
2010 15 60.0 42 21 50.0 7 33.3 0.17
2011 15 86.7 45 36 80.0 11 30.5 0.24
2012 7 71.4 21 15 71.4 9 60.0 0.43
2013 21 52.4 58 30 51.7 15 50.0 0.26
2014 45 44.4 108 54 50.0 15 27.8 0.14
2015 49 61.2 131 80 61.1 19 23.8 0.15
2016 42 54.8 95 48 50.5 20 41.7 0.21
2017 46 45.7 119 56 47.1 23 41.1 0.19
2018 50 42.0 137 52 38.0 14 26.9 0.10
2019 35 37.1 83 33 39.8 15 45.5 0.18

The National Park Service shall not be held liable for improper or incorrect use of the data described and/or contained herein. These data and related graphics (if available) are not legal documents and are not intended to be used as such. The information contained in these data is dynamic and may change over time. The National Park Service gives no warranty, expressed or implied, as to the accuracy, reliability, or completeness of these data. For more information: https://www.nps.gov/disclaimer.htm

Point Reyes, Point Reyes National Seashore, bird, birds, plover, plovers, snowy plover, snowy plovers, western snowy plover, western snowy plovers, Charadrius nivosus, Charadrius nivosus nivosus



Last updated: October 7, 2019

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