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.
| 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 |
| 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 |
| 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 |
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