Determining Breeding Areas and Migration Routes of Coastal

Determining Breeding Areas and Migration Routes of Coastal Northwest Sooty Fox Sparrows (Passerella iliaca unalaschcensis ) Over-Wintering on Vancouver Island using Geolocators

Summary

The phylogeography of the Fox Sparrow ( Passerella iliaca ) has been much debated, but birds breeding along the west coast of North America are generally considered to be a separate species ( Passerella iliaca unalaschecensis ) based on mitochondrial DNA. Using plumage characteristics, a further seven sub- species have been identified within this group. These subspecies, and their migration patterns, have become an emblematic example of leap-frog migration, based upon the early work of Swarth (1920). However, more recently, these connectivity patterns have been called into question, partly based on the relative difficulty in accurately distinguishing plumages and subspecies in the field. Light-level geolcators are now small enough to be carried by <50 g songbirds and can reveal remarkable new insights into migration patterns and behaviour. Using geolocators, we will track a population of Fox Sparrows overwintering on southern Vancouver Island to their breeding areas. The objectives of this study are two-fold: 1) Based on leapfrog patterns identified by Swarth (1920) we will use direct-tracking methods to test the hypothesis that birds overwintering on Vancouver Island breed on the island and do not mix with birds along the northwest coast (i.e. strong connectivity) and 2) Identify connections between overwintering and breeding areas that are important to conservation and management of Fox Sparrow populations.

Personnel

• Project Leader: Michael Simmons, Rocky Point Bird Observatory (RPBO) • Migration Research Advisor: Dr. Bridget Stutchbury, York University • Science and Geolocator Technical Advisor and Data Analyst: Dr. Kevin Fraser, York University • Vancouver Island Science Advisors: Bruce Cousens, M.Sc., R.P.Bio., BC Purple Martin Stewardship & Recovery Program, and RPBO, and Dr. Jonathan Moran, Royal Roads University and RPBO • Field Leader: Ann Nightingale, RPBO

Introduction and Background

The Fox Sparrow ( Passerella iliaca ) is divided into four groups on the basis of mitochondrial DNA and corresponding plumage characteristics (Zink, 1994). Only one of these groups is found in coastal BC, i.e., the Coastal Northwest Sooty Fox Sparrow ( P. i. unalaschcensis ); within this group seven sub-species are recognized (Pyle, 1997). Breeding ranges and southward migration to over-wintering areas have been identified for these sub-species (Swarth, 1920; Figure 1).

Breeding areas are shown with solid blue lines.

Wintering areas are surrounded with dashed lines.

Presumed migration routes link breeding and wintering areas.

P.i. fuliginosa winters within the breeding area

Figure 1: Map from Swarth, 1920

Leap-frog migration in the Sooty Fox Sparrow was first described by Swarth (1920), and the concept was refined by Bell (1997; Figure 1). Simply put, the most northerly breeders winter the furthest south. The most southerly breeder ( P. i. fuliginosa ) breeds in SE Alaska, on the west coast of Vancouver Island and in immediately adjacent areas of Washington State. The map of leap-frog migration created by Swarth (1920) shows six sub-species and their migration patterns, Figure 1, above. According to Bell (1997):

“The status of this distribution as the exemplar of leap-frog migration patterns is to some extent unfortunate because, although there are elements of a leap-frog pattern in this distribution, a number of factors confound both the leap-frog pattern and its interpretation. For instance, the breeding areas of populations which winter in southern California are only marginally the most distant from the wintering area, a fact which is not immediately obvious from the illustration used in Swarth's (1920) paper, and frequently reproduced elsewhere (e.g., Faaborg 1988, Welty and Baptista 1988), because of the orthographic projection used. One of these populations, P. i. unalaschcensis , has a breeding distribution with a latitudinal range similar to that of P. i. townsendi which winters much further north, and P. i. insularis and most P. i. unalaschcensis breed to the south of P. i. annectens which also has a relatively northern wintering range.

Ignoring the three western subspecies, a leap-frog pattern can be discerned among P. i. annectens , P. i. townsendi and P. i. fuliginosa … “

Bent (1968) describes the difficulty of field identification of the sub-species:

Adjoining races inter-grade wherever their ranges meet, and the differences between some forms are so slight that the practicality of such fine splitting is sometimes questioned. For instance George Willett (1933) states his "personal feeling is that we are attempting to recognize too many races of Passerella and that the situation might be greatly clarified by uniting some of the most closely allied forms." He suggests that uniting insularis and sinuosa with unaIaschcensis , "would greatly simplify the classification of the group." Gabrielson and Lincoln (1959) state: "It is not possible, however, to accurately identify [the Alaskan subspecies] in the field except as Fox Sparrows. All are large sparrows with dark brown or grayish brown backs with very heavily streaked under-parts.”

Over-wintering sub-species of Coastal Northwest Sooty Fox Sparrows on Southern Vancouver Island may include the following:

• P.i. unalaschcensis ; • P.i. sinuosa ; • P.i. townsendii ; and • P.i. fuliginosa .

Linsdale (1928) highlighted variations in the skeletons of these sub-species that appear to be related to migration:

“In every case the samples with large bones in the wings and pectoral girdle belong to races which have long migration routes and the samples with those bones weakly developed belong to relatively sedentary races.”

Differentiation of the sub-species is difficult in the field and in the hand. Wintering birds in southern Vancouver Island have not been differentiated by RPBO and it is assumed that most of these birds are P. i. fuliginosa . We do know that almost all Fox Sparrows observed in southern Vancouver Island are of the Coastal Northwest Sooty group. A very few birds are of the interior Slate-coloured group and very rarely birds of the Red group are seen (Cruikshank, personal communication). For this project we will only use birds of the “Sooty” group.

Fox Sparrows can be found throughout the Greater Victoria area during the winter months and are common in backyards and on the ground near feeding stations. The highest density of Fox Sparrows recorded during a Christmas Bird Count in the Victoria count circle was 923, and in 2011, the total was 899 (Christmas Bird Counts, Victoria Natural History Society, BC). The closest known breeding area is about 60km from Victoria, near Shirley, west of Sooke. (BC Breeding Bird Atlas, 2008-2012). These observations suggest that at the very least, there is a considerable short-distance migration.

RPBO fall migration records show that there have been 59 returns of Fox Sparrows in later years since 1994. Of the returning birds, 27% return for two years, 15% return for three years, and one bird has returned and been recaptured for five successive years. In one remarkable year (1998), 16 of the Fox Sparrows banded returned in subsequent years, including the five-year veteran.

Even though the fall migration monitoring season at Rocky Point ends relatively early for returning Fox Sparrows, we believe that these birds are returning to use Rocky Point as their wintering area. Evidence for this assertion is that once Fox Sparrows return, the individual birds are often recaptured several times. This leads us to believe that they are winter residents rather than transient migrants.

Fox Sparrows as Candidates for Geolocator Use

Southern Vancouver Island is a wintering area for a great number of species that breed elsewhere. However, the routes by which this concentration of winter species disburse to breeding areas to the north and east, remain unknown. Significant concentrations of the Coastal Northwest Sooty Fox Sparrow winter in southern Vancouver Island and this typically west coast species is known to breed over a wide coastal range to the north (Figure 1). There is no known nesting in the immediate vicinity of Victoria, but breeding has been reported in other areas of Vancouver Island. The introduction of relatively low cost geolocators that can be attached safely to smaller birds provides the first opportunity to identify breeding locations and migration routes for passerines that winter here. If successful, we anticipate being able to use this approach to identify the migration pathways of many other Pacific coast species.

Survival rates of wintering sparrows, including the Fox Sparrow, were investigated over a period of 13 years at the Coyote Creek Field Station in northern California (Sandercock, B.K., and Jaramillo, A., 2002). The key findings of this and other studies that have implications for the proposed project are as follows:

• “Winter site fidelity is higher for after hatch year (AHY) birds than for hatch year (HY) birds”; • “Site fidelity of migratory sparrows appears to be flexible among immature birds but becomes fixed with increasing age”; • “Site fidelity is often strong once a wintering area is selected (Ralph and Mewaldt, 1976)”; • “Immature sparrows of subdominant status may have higher mortality during winter or subsequent migration periods”; • “Survival rates of sparrows are apparently constant once a bird becomes an adult (Baker et al ., 1981; and Nol and Smith, 1987). Site-faithful individuals have similar rates of local survival in the six taxa studied, which included Fox Sparrows (0.35); the highest survival was observed in Song Sparrows (0.56)”; and • “Fidelity to breeding sites is affected by genetic considerations related to mate selection, and by ecological factors such as local knowledge of food and predator dispersion. In contrast, fidelity to wintering sites should be determined by ecological factors alone, unless pairing occurs at non breeding areas, as in waterfowl (Robertson and Cooke, 1998). For at least some migratory land birds, site attachment is stronger at wintering sites than at breeding areas (Holmes and Sherry, 1992)”.

In order to access geolocator information, the unit must be recovered after a migration cycle. Therefore, winter site fidelity is crucial to success. As geolocators are expensive, it is important to deploy them in a manner that maximizes the likelihood of recovery. We propose the following general approach (details in the following “methodology” section) for geolocator deployment:

• Fox Sparrow individuals are in their second winter or later; • Geolocator application occurs as late in the winter as possible; • Capture (and recapture) site locations are chosen where repeated observations are easily achievable throughout the winter; and • Geographically dispersed sites are chosen throughout southern Vancouver Island.

The first geolocators would be attached to over wintering Fox Sparrows in January 2013 and recovered as soon as possible after the birds return to their wintering areas, in November 2013 or later. Data analysis would then be possible during the winter of 2013-14.

Geolocator Technology

We propose to use British Antarctic Survey Mk 10S geolocators, with the following geolocator specifications:

• Size: 18 x 9 x 6 mm • Weight: 1.1 g • Light resolution recording: 10 min. • Harness as described by Fox (2010): “Studies to date have shown that …. a leg-loop harness based on the Rappole-Tipton harness is suitable for most terrestrial birds…. Depending on species …. the maximum ratio for back mounting is considered to be 3-5%”

As the median weight of Fox Sparrows captured at Rocky Point in the fall is 33gm and the total weight of Mk 10 geolocators and harness is 1.2gm the ratio of backpack weight to bird weight would be 3.6%.

We would use the modified Teflon harness employed for songbird migration research, as reported by our partners at York University (Stutchbury et al ., 2009).

Proposed Methodology

1. Introduction

Fox Sparrows usually return to southern Vancouver Island in October. End of winter departure dates are not exactly known but are probably in late March and April. While the density in the Greater Victoria area is high the numbers in any one location are small, suggesting there may be feeding territories established in the winter. It is believed that the same birds occupy the same territory the entire winter and occupy the same area in subsequent winters.

It is known that Fox Sparrows average a 35% annual survival rate after hatch year (Sandercock and Jaramillo, 2000). Also, after the first winter, strong site fidelity is established. We propose therefore to

select AHY (After Hatch Year) birds in their second or subsequent winters. Birds captured at Rocky Point are predominantly hatch year birds (> 80%) and we assume that the population of winter resident birds in southern Vancouver Island is structured similarly. This means a large number of birds will need to be trapped to obtain sufficient numbers of suitable adult birds.

2. Testing the Harness

It has recently been reported (Seavy, 2011) that seven of eleven (64%) Golden-crowned Sparrows returned to an over wintering site where geolocators had been attached in good condition but without the geolocators. It is thought that the kevlar threads of the harness attachment had lost strength due to exposure to sunlight and/or other atmospheric effects. Although we will use the more sturdy Teflon harness designed at York University there is a need to test it with Fox Sparrows. Early in the winter, soon after the birds arrive at overwintering sites, we propose to attach dummy replica geolocators with the Teflon harnesses and monitor them until early January before attaching geolocators. If the harness deteriorates we will need to reconsider.

3. Testing for Effects on Performance

We also need to understand whether the attachment of geolocators to birds affects their behavior. Previous work on other species has not demonstrated any deleterious effect but we believe that establishing a control group would provide some evidence on whether or not deleterious effects (from either the geolocator itself or from the backpack) are experienced by Fox Sparrows. This control group would be colour banded. The control group will only be established if a sufficient number of mature (AHY – after hatch year) birds are captured.

It has also been proposed that a second control group should be created to test the idea that the ability of migrating birds to navigate might be affected by steel in the batteries powering the geolocators. This does not seem to have been a factor in any previous species fitted with geolocators.

To create a control group we have to assume there are sufficient AHY birds available. If there are insufficient AHY birds available neither control group will be created. If sufficient birds are available we will use the birds which have been fitted dummy geolocators early in the winter, as a control group. The decision on whether or not to remove the dummy back packs from these birds will be taken in January.

4. Colour Bands

To track both the geolocator and control group birds during the winter, and to identify returning birds, colour bands will be installed on all birds.

Three groups will be established:

I. Birds captured at any time in the project which are determined to be HY (Hatch Year) birds, II. AHY birds captured early in the winter and fitted with dummy backpacks (they need to be recaptured in January to examine the harness condition), III. AHY birds fitted with geolocators.

We propose to use fluorescent paint on numbered bands for group (1).

Group two will have a plastic colour band in addition to the numbered band.

Group three will also have a colour band (different colour !) in addition to the numbered band.

The purpose of the colour banding is to make it easy to identify and recapture birds in each group. There will not be a unique colour banding scheme for each bird. Once in the hand individuals can of course be identified by number.

5. Increasing Positional Accuracy

5.1 Parallel measurements from geolocators at fixed locations

Geolocators run in stationary control situations for off-bird static calibration can be surprisingly accurate when shading effects are eliminated or controlled and daily position estimates are averaged or otherwise analysed over time. For example, “with about 2 weeks of static pre- calibration data we have been able to estimate the known static pre-calibration location with a linear error of <20 km; std. error estimates are on the order of 0.2° lat/long” (Cousens, personal communication).

Two geolocators will be deployed at fixed locations from the time of installation of geolocators on birds until the presumed departure time. These two static geolocators may then be deployed near the presumed west coast Vancouver Island breeding areas for the duration of the breeding season.

5.2 Avoid dependence on Equinox period

Attach geolocators at least six weeks before the Equinox “black-out” period (March 1 – April 10) to enable calibration with fixed location geolocators and before the black-out period in which latitude cannot be accurately determined.

5.3 Live pre-departure downloads

Sun elevations derived from static calibrations are 2-3 degrees lower than when determined from the bird itself. Live downloads (from birds wearing geolocators) are therefore infinitely more useful. Assuming the live-download data can be pooled, the advantage is that the sample size is much greater than if the same data is downloaded when the geolocators are recovered the following winter. This is because the number of geolocators recovered will likely be about 30% - 40% of all that are installed. As we are uncertain of the effects of re-trapping birds on several occasions we will leave the live down-load possibility as a desirable but not essential component of the research.

5.4 Post recovery calibration

A static position accuracy check will be done for a 1-2 week period, off-bird after recovery that will also confirm low light transition threshold performance free of any cover shading effects. This presumes the logger is still running.

6. Sexing the birds

Determining sex by plumage is not possible. Therefore taking blood or feathers is considered. It is possible that males and females may use different migration routes or, more probably, migrate at different times. It is also possible that behavioral differences may make positional information from geolocators on males more accurate than from those on females. Either blood samples or feathers will be obtained from all birds fitted with geolocators to determine sex and possibly for stable isotope analysis to determine possible areas of natal origin.

7. Number of Deployment sites

It is preferable to minimize the number of deployment sites to:

i. Increase the probability of recovery, and ii. Reduce the effort required.

However the number of suitable birds at any one site is not large. Fox Sparrows seem to be territorial in winter (defending feeding habitat). A large proportion of the wintering population is hatch year birds which have not yet firmly established a wintering site and are not suitable candidates.

During the first winter we need to be able to regularly observe the birds’ behavior with respect to; tolerance of the harness and dummy backpack, site fidelity, and survival. Later in the winter, after installation of the geolocators, we also need to continue observing behavior and to record when they depart, for calibration purposes. When the birds return the deployment sites need close surveillance to maximize the chance of geolocator recovery and for observation and recapture of control group birds.

We will use backyards with suitable habitat for deployment and we expect only one or, at the most, two suitable birds at each backyard. As we need dedicated observers rather than adjacent neighbours with only casual interest, we have defined “site” as an area with a number of dedicated backyards that could encompass as much as a 20km circle. The proposed Victoria sites are shown in figure 2. Twenty sites have been tentatively identified in Victoria.

We propose to use two geographically separated sites; Victoria and Nanaimo with 20 geolocators deployed in Victoria and 10 in Nanaimo. Recoveries in Nanaimo would be expected to be 3 or 4 and double that number in Victoria, assuming a typical annual survival rate of 35%.

Figure 2 Proposed Geolocator Deployment Sites in Greater Victoria

Ethical Care and Permits

RPBO holds a banding permit that allows banding of passerines, hummingbirds and owls. It needs to be extended to include:

Colour banding, Installation of geolocators, Capture of birds using ground traps, and Obtaining blood samples from recaptured birds.

The application has been made to the Bird Banding Office at Environment Canada.

To publish our results, we need certification from an Animal Care Committee. Fox Sparrow and the Vancouver Island field location will be added to the York University Animal Care Protocol – Number: 2009-2 W (R1).

Literature Cited Baker, M.C. et al. (1981) Demography of White-crowned Sparrows ( Zonotrichia leucophrys nuttalli ). Ecology 62 : 636–644.

Bell, C.P. (1997) Leap-frog migration in the fox sparrow: minimizing the coast of spring migration. Condor 99 (2):470-477.

Bent, A. C. (1968) Life histories of North American cardinals, Grosbeaks, buntings, towhees, finches, sparrows, and allies. U.S. Natl. Mus. Bull. 237 : 1889.

British Columbia Breeding Bird Atlas (2011) Bird Studies Canada. . www.birdatlas.bc.ca/bcdata/maps.jsp

Fox, J.W. (2010) British Antarctic Survey Geolocator Manual v.8, Cambridge, UK. Accessed at www.birdtracker.co.uk

Holmes, R.T. and Sherry, T.W. (1992). Site fidelity of migratory warblers in temperate and Neotropical wintering areas: Implications for population dynamics, habitat selection, and conservation. 563–575 in Ecology and Conservation of Neotropical Migrant Landbirds (J. M. Hagan III and D. W. Johnston, Eds.). Smithsonian Institution Press, Washington, D.C.

Linsdale, J.M. (1928) Variations in the fox sparrow ( Passerella iliaca ) with reference to natural history and osteology. Univ. Calif.Pub. Zool. 30 (12): 377-383.

Nol, E. and Smith, J.M.N. (1987) Effects of age and breeding experience on seasonal reproductive success in the Song Sparrow. J. Anim. Ecol. 56 :301–313.

Pyle, P. (1997) Identification Guide to NA Birds. Slate Creek Press, Bolinas, CA. 1: 577-579.

Robertson, G.J. and Cooke, F. (1998) Winter philopatry in migratory waterfowl. Auk 116 :20–34.

Ralph, C.J. and Mewaldt, L.R. (1976) Homing success in wintering sparrows. Auk 93 :1–14.

Sandercock, B.K., and Jaramillo, A. (2002) Annual survival rates of wintering sparrows: assessing demographic consequences of migration. Auk 119 : 149-165.

Seavy, N.E., et al (2011) Establishing the Breeding Provenance of a Temperate Wintering North American Passerine, the Golden Crowned Sparrow, Using Light-level Geolocators. PLoS ONE7 (4): e34886.

Stutchbury, B.J.M. et al . (2009) Tracking Long-Distance Songbird Migration by Using Geolocators. Science 323 (5916):896.

Swarth, H.W. (1920) Revision of the avian genus Passerella with special reference to the distribution and migration of the races in California. Univ. Calif. Publ. Zool. 21 : 75-224.

Zink, R.M. (1994) The geography of mitochondrial DNA variation, population structure, hybridization, and species limits in the fox sparrow ( Passerella iliaca ). Evolution 48 (1): 96-111.