Site fidelity of a coastal cactus wren (Camphylorynchus brunneicapillus) on the Palos Verdes Peninsula.
Recently, two independent investigations have converged to demonstrate a remarkable instance of site fidelity by a single individual. During 2012 and 2013, biologists from the U. S. Geological Survey sampled 620 coastal cactus wrens in Ventura, Los Angeles, San Bernardino, Riverside, Orange, and San Diego Counties to assess the impacts of habitat fragmentation using contemporary genetic analysis (Barr et al. 2015). Birds that were captured for the genetic analysis were banded to prevent re-sampling individuals (1). A total of eight individuals were captured and banded in the Preserve during the second year of this study. Each individual's location and band number was recorded at capture and blood was drawn for the genetic analysis.
In 2014, the Palos Verdes Peninsula Land Conservancy (Conservancy) initiated a Citizen Science Cactus Wren program to utilize volunteers to observe the coastal cactus wrens within the Preserve. The Conservancy manages and restores habitat within the Preserve for several special status species, as well as the coastal cactus wren. The program was designed to return information about how the wrens utilized their habitat, within both existing habitat and newly established areas of habitat. This is important information for the Conservancy in its mission to restore cactus stands within the Preserve's coastal sage scrub habitat.
The volunteers conducted weekly surveys within the Preserve's Alta Vicente Reserve from March through July during the breeding seasons in 2014 and 2015. The surveys were conducted for 20 minute periods at specifically delineated territorial polygons within areas referred to as West and East (Fig. 1). Observations were recorded by the minute and included number of cactus wrens (adult, juvenile, or unknown), presence of predators, and several qualitative behavior patterns from which frequencies could be computed (Table 1). For these surveys, the enthusiastic volunteers took to the field outfitted with binoculars, spotting scopes, and cameras equipped with telephoto lenses.
That coastal cactus wrens spend most of their time moving within the cactus thickets, rising above the cactus for only brief moments, is reflected by the data collected by the Citizen Science volunteers in 2015. Aural and visual cactus wren observations occurred at a combined frequency of 6.0% (Table 1). Birds were observed flying into or out of their territories during 2.3% of the observations, whereas activities related to rearing their brood were observed during 1.0% of the observations.
Variations in the throat and breast patterns were used by Citizen Science volunteers to track individuals. In 2014, after witnessing a pair copulate in the West, their distinctive color patterns enabled the volunteers to determine the birds' respective sex. Subsequently, the volunteers tracked the behavior of the pair through their courtship, nesting, and the successful rearing of two chicks. Throughout the nesting season, vocalization and defensive behaviors were primarily the domain of the male while the female tended to the nest and chicks. After fledging, one chick was witnessed mimicking its father's boisterous defensive calls, leading to the conclusion that the young individual was also male.
During the 2015 survey, one of the volunteers captured photos of a wren in the East at polygon AV03c. When processing the photos later that day at home, she noticed that the bird was banded with a single, silver band on its left, lower leg (Fig. 2). Similarly, I photographed the same individual four weeks later on July 4, 2015 in polygon AV03f, and only noticed the band in the photographs, for it was not visible with the naked eye or with binoculars. Each band has a unique number, but unfortunately, the number on the band could not be discerned in any of the photographs.
Earlier in 2013, two cactus wrens captured in polygon AV03c were banded with silver bands on their lower left leg, one a female and the other unknown (Table 2). Due to the obscured band number in the individual photographed during the Citizen Science surveys, we could not directly determine which bird from the 2013 banding effort was being observed. However, the banded individual's behavior indicated that it was a male. The bird was very noisy, acting defensively in the presence of Citizen Science observers. It moved away from its youngsters that were foraging nearby, circling around to perch on a tree tobacco (Nicotiana glauca), and vocalize defensively. This was behavior very similar to that displayed by the male observed in 2014 by the Citizen Science observers. Based upon the similar behavior, it was concluded that this bird in the East, originally marked as an unknown at the time of banding, was certainly a male. Scarlett Howell (USGS, personal communication) concurred that this behavior is characteristic of males and that the banded bird was likely the individual identified by them as unknown in Table 2.
The banded bird observed during the 2015 survey was seen at locations throughout the east, including the same polygon where it was banded and later photographed (AV03c). In May, this male was observed foraging for its nestlings, flying out of polygon AV04a into farmed cactus and back to the nest. Later in June, both adults were observed leading their chicks out of their natal area (AV04a) and into a farmed patch of cactus (Opuntia ficus-indica). Through June and July, the family was frequently observed in the vicinity of the very polygon in which the male was captured for banding.
Two years after banding, this male was operating in the very same area that it was originally captured, exhibiting a remarkable degree of fidelity to the site. Although cactus wrens are known to be a sedentary species, rarely flying more than one km in distance (Rea and Weaver 1990), this observation provides supporting evidence that this species is indeed, a sedentary bird.
This observation was the result of the effort of many. I thank the Palos Verdes Peninsula Land Conservancy's encouragement of research within the preserves that it manages and foresight for creating the Citizen Science program. Much admiration is extended to the USGS biologists who spent two years capturing the birds for sampling and banding while getting closer to cactus than anyone would prefer. Additionally, they provided critical support in preparing this manuscript. Finally, much appreciation is extended to the Citizen Science volunteers who brought their dedication and passions to the field:
2014 Team: Helen Ashford, Bonnie Cohn, Bill Cullen, Joyce Daniels, Rina Gardner, Donna McLaughlin, Evi Meyer, Linda Wedemeyer, and Lowell Wedemeyer.
2015 Team: Phil Carnehl, Bonnie Cohn, Vanessa Cruz, Joyce Daniels, Joan Krause, Donna McLaughlin, Harry McWatters, Mai Lee, Evi Meyer, Nancy Fitzhugh, Marty Lewis, Alex Retana, Lauren Singleton, and Pete Verenkof.
Kelly R. Barr, B.E. Kus, K.L. Preston, S. Howell, E. Perkins, and A.G. Vandergast. 2015. Habitat fragmentation in coastal southern California disrupts genetic connectivity in the cactus wren (Campvlorhynchus brunneicapillus). Mol. Ecol. 24:2349-2363.
Rea, A.M. and K.L Weaver. 1990. The taxonomy, distribution, and status of coastal California cactus wrens. Western Birds 21(3). 126 pp.
Palos Verdes Peninsula Land Conservancy, 916 Silver Spur Road, Suite 206, Rolling Hills Estates, CA 90274, USA, email@example.com
(1) Barr, K. R., A. G. Vandergast, and B. E. Kus. 2013. Genetic structure in the cactus wren in coastal southern California. U.S. Geological Survey, Reston, VA. 27 pp. Available from: https://nrm.dfg.ca.gov/FileHandler. ashx?DocumentID=65007 via the Internet. Accessed 20 February, 2016.
Caption: Fig. 1. Alta Vicente West and East are shown in yellow in the upper left-hand box. The territorial polygons are shown in the large map. The farmed cactus is visible as even rows adjacent to polygon AV04a.
Caption: Fig. 2. Adult male photographed on 6 Jun 2015 that was banded two years earlier on 12 Jun 2013 as an unknown sex. Image courtesy of Mai Lee.
Table 1. All observations from the 2015 Citizen Science Cactus Wren Program from 230 twenty-minute surveys at 21 territories at Alta Vicente Reserve from 21 Feb 2015 through 25 Jul 2015. Each territory was observed for 20 minutes and observations recorded by the minute. Occasionally multiple observations occurred within a 1-minute observation interval. 2015 Type of observation Count Percent No observation 4101 88.98 Audio observation 65 1.41 Visual observation 213 4.62 Predator observed 32 0.69 Flight out to a different territory 77 1.67 Flight in from a different territory 73 1.58 Defensive/aggressive activity 2 0.04 Copulation 0 0.00 Nesting material in beak 15 0.33 Flight into nest 16 0.35 Flight out of nest 13 0.28 Feeding young in nest 1 0.02 Feeding young out of nest 1 0.02 Total observation intervals 4600 -- Table 2. List of cactus wrens captured that were banded at the Alta Vicente Reserve following blood drawn for genetic analysis during the 2012-2013 USGS field effort (from B. Kus (USGS personal communication). All coordinates are in WGS84. Site Date banded Age/Sex Latitude AV1c 30-Jul-12 Hatch year/Unk 33.74402 AV2c 30-Jul-12 Hatch year/Unk 33.74411 AV03c 12-Jun-13 Adult/Unk 33.74257 AV04a 12-Jun-13 Adult/Female 33.74401 AV04a 12-Jun-13 Adult/Male 33.74401 Site Longitude Band ID * AV1c -118.40582 DGDG/YEYE : WHWH/Mre AV2c -118.40117 DGDG/YEYE : YEYE/Mre AV03c -118.40328 -/Msi : -/- AV04a -118.40144 -/Msi : -/- AV04a -118.40144 -/- : /-Msi * Top Left Leg/Bottom Left Leg : Top Right Leg/Bottom Right Leg. Metal bands: Mre = federal red anodized aluminum band, Msi = federal silver aluminum band. Darvic bands: DGDG = dark green, WHWH = white, YEYE = yellow.
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|Publication:||Bulletin (Southern California Academy of Sciences)|
|Date:||Dec 1, 2016|
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