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The Incidence and Effects of Ticks on Migrating Birds at a Stopover Site in Maine
Sara R. Morris, Miranda C. Ertel, and Mary P. Wright

Northeastern Naturalist, Volume 14, Issue 2 (2007): 171–182

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2007 NORTHEASTERN NATURALIST 14(2):171–182 The Incidence and Effects of Ticks on Migrating Birds at a Stopover Site in Maine Sara R. Morris1,2,*, Miranda C. Ertel1, and Mary P. Wright2 Abstract - Ticks are common ectoparasites on birds, but little work has examined the effects of ticks on migrating birds. In this study, we examined the incidence of ticks on migrants during spring and fall migration on Appledore Island, ME. Because ticks are not indigenous to the island, birds with ticks are very likely to have transported them from elsewhere. During spring, 2.4% of migrants captured were parasitized by at least one tick, whereas during fall, 0.6% of migrants were parasitized by ticks. These trends occurred in several of the commonly captured species, although there was substantial variation among species. The average number of ticks per infested bird did not differ between the seasons among our commonly captured species. Males and females had similar tick loads within most species. We did not find a consistent pattern of difference in condition (fat and mass) among birds that were parasitized by ticks compared with those that were not. Furthermore, comparison of birds parasitized by ticks with those that were not indicated no significant difference in either the recapture rate or the stopover length between these two groups. Although parasites may greatly impact the fitness of individual birds, our results suggest that ticks are not impacting the species of migrant birds that use this stopover site during migration. Introduction Ticks are common ectoparasites on birds. A number of studies have documented negative impacts of tick infestation on a variety of measures of breeding success, including incubating success (Mangin et al. 2003), rates of growth by nestlings (Bosch and Figuerola 1999, Morbey 1996, Ramos et al. 2001), nestling mortality (Bergström et al. 1999, McKilligan 1996, Ramos et al. 2001), and recruitment and site fidelity (Boulinier and Danchin 1996, cf. Gauthier-Clerc et al. 2003). Despite the documentation of negative effects of ticks on birds during the breeding season, little is known about the effects of ticks at other times in the annual cycle. Migrant birds regularly host a variety of ticks. Numerous species of migrant birds parasitized by ticks have been documented in Alabama and Georgia (Kinsey et al. 2000), Connecticut (Stafford et al. 1995), Maine (Rand et al. 1998, Smith et al. 1996), and Wisconsin (Weisbrod and Johnson 1989). The precise bird species hosting ticks varied among these locations. Previous work in New England has documented Ixodes 1Department of Biology, Canisius College, 2001 Main Street, Buffalo, NY 14208. 2Shoals Marine Laboratory, Cornell University, Ithaca, NY 14853. *Corresponding author - morriss@canisius.edu. 172 Northeastern Naturalist Vol. 14, No. 2 scapularis Say (deer tick), I. brunneus Koch, I. muris Bishopp & Smith, I. dentatus Marx, Amblyomma maculatum Koch, Dermacentor variabilis Say, and Haemaphysalis leporispalustris Packard on migrant birds (Smith et al. 1996, Stafford et al. 1995). Stafford et al. (1995) reported that 94.4% of over 4000 ticks on birds were deer ticks in their study in Connecticut involving both migrants and summer residents. In Canada, Scott et al. (2001) and Morshed et al. (2005) found that Ixodes ticks were on more than half the migrant birds parasitized by ticks. Most ticks found on birds are subadults, including nymphal and larval stages (e.g., Kinsey et al. 2000, Morshed et al 2005, Smith et al. 1996, Stafford et al. 1995), that often remain on the birds for two to four days. Although ticks are regularly found on birds during migration, the effects of ticks on migrating birds have not been documented. This project had two goals. The first goal was to compare the frequency of migrating birds parasitized by ticks during spring and during fall. The second goal was to compare birds with and without ticks during migration to determine if the presence of ticks had a negative impact on the birds. We hypothesized, first, that birds parasitized by ticks would be more prevalent, and would have more ticks, during spring than fall because they are arriving from areas of higher tick densities; and second, that birds parasitized by ticks would be in diminished condition, have a greater likelihood of recapture, and have longer stopovers compared with birds that were not parasitized by ticks. Methods This study was conducted on Appledore Island, ME (42.97°N, 70.62°W), which is the largest island in the Isles of Shoals, a group of nine rocky islands and numerous ledges located approximately 10 km southeast of Portsmouth, NH. Scrub/shrub is the dominant terrestrial habitat on this 38.5- ha island. Additional local habitats include small marshes, low trees, and open fields. Previous work by Smith et al. (1996) found no ticks on the two species of mammals on the island, no questing nymphs on vegetation in June, and low numbers of questing adults in October, which suggests that ticks are not indigenous to the island; thus, most ticks on birds were likely to be transported from other sites. Migrating birds were captured using mist nets (12 m, 30-mm mesh) on Appledore Island from 1990 to 2002. Spring banding generally occurred from early May to mid-June, and fall banding generally occurred from mid- August until late September or early October (Table 1). Volunteers captured birds in 6–10 nets, which were opened before sunrise, closed after sunset, and checked every twenty minutes. Nets were not open in inclement weather. To reduce the likelihood of injury to birds, nets were set about 0.5 m above the ground, thus potentially missing some ground-foraging birds. 2007 S.R. Morris, M.C. Ertel, and M.P. Wright 173 All birds were taken to a central location for banding. For each bird banded, we recorded age, sex, wing chord (0.5 mm), tail length (0.5 mm), tarsus length (0.1 mm), fat (categories ranging from 0 = no fat to 4 = fat bulging), and mass (0.01 g). During the banding process, all birds were examined for ticks, especially around the bill, eyes, and chin, because ticks are often concentrated on the head, throat, and neck of migratory birds (Scharf 2004, Stafford et al. 1995). As part of a study on infectious diseases, all ticks were removed from the birds. For any bird parasitized by ticks, we recorded the presence and number of ticks on the bird. Statistical analyses were performed using the five species of birds that most commonly hosted ticks between 1990 and 2002 (Table 2). For each species, we compared the proportion of birds parasitized by ticks and the average number of ticks on individual birds during the two seasons. To determine whether the presence of ticks was impacting the migration and stopover ecology of migrants, we compared the fat, mass, condition (mass*100/wing; following Winker 2005), proportion recaptured, and stopover duration between birds parasitized by ticks and those that were not. Additionally, we investigated whether ticks affected male and female Common Yellowthroats (scientific names are given in Table 2) differently. Likelihood-ratio chi-squared tests were used to compare the proportion of birds with ticks between seasons, sexes, and recapture categories. Two sample t-tests were used for all other analyses. All analyses were performed in SYSTAT 10.2. All significant P-values reflect sequential Bonferroni correction for multiple tests. Table 1. Summary of seasonal banding effort on Appledore Island, ME. Spring Fall Number % Number % Net- of birds with Net- of birds with Year Dates of banding hoursA captured ticks Dates of banding hoursA captured ticks 1990 18 May–8 June 1777 1445 0.8 16 Aug–20 Sept 2970 1258 0.2 1991 15 May–6 June 1766 1967 0.9 16 Aug–21 Sept 2895 1464 0.5 1992 2 May–31 May 2428 2482 2.3 15 Aug–20 Sept 2652 1432 0.3 1993 8 May–5 June 2407 2399 1.0 14 Aug–22 Sept 3181 1045 1.1 1994 30 April–4 June 3461 2528 1.3 13 Aug–7 Oct 5804 2672 0.3 1995 29 April–8 June 4550 3480 2.5 15 Aug–8 Oct 5993 2673 0.9 1996 6 May–8 June 3513 2230 1.0 15 Aug–30 Sept 3697 2017 0.4 1997 6 May–9 June 3382 1996 3.0 15 Aug–24 Sept 4696 1684 1.0 1998 7 May–9 June 3929 3224 3.8 15 Aug–30 Sept 5284 2260 0.6 1999 6 May–9 June 4103 2636 3.6 15 Aug–1 Oct 5038 1998 0.2 2000 3 May–9 June 4093 2533 2.2 15 Aug–1 Oct 4872 2317 0.9 2001 3 May–10 June 4494 2684 2.1 15 Aug–3 Oct 5188 2565 0.9 2002 6 May–9 June 3591 2519 4.6 15 Aug–1 Oct 4716 1892 0.5 ANet-hours are a measure of effort; 1 net-hour = one 12-m net open for one hour. 174 Northeastern Naturalist Vol. 14, No. 2 Table 2. Incidence of ticks collected from migrants on Appledore Island, ME. Comparisons between seasons were performed only on the five species most likely to be parasitized by ticks (indicated with*). Data from 1990 to 2002 were pooled. Spring Fall Mean Mean Common name NA %B NC (± S.D.)D RangeE NA %B NC (± S.D.)D RangeE Sharp-shinned Hawk, Accipiter striatus Vieillot 6 0.00 23 4.35 1 1.00 1 Northern Flicker, Colaptes auratus Linnaeus 20 0.00 358 0.28 1 1.00 1 Yellow-bellied Flycatcher, Empidonax flaviventris Baird & Baird 379 0.00 420 0.24 0 Traill’s = Alder Flycatcher and Willow Flycatcher, 391 0.26 1 1.00 1 468 0.00 Empidonax alnorum Vieillot & E. traillii Audubon Red-eyed Vireo, Vireo olivaceus Linnaeus 1536 0.13 1 2.00 2 2853 0.00 House Wren, Troglodytes aedon Vieillot 59 5.08 3 2.67 ± 2.89 1–6 19 0.00 Golden-crowned Kinglet, Regulus satrapa Lichtenstein 10 0.00 645 0.16 0 Veery, Catharus fuscescens Stephens 240 7.50 17 2.71 ± 2.44 1–8 161 1.86 2 1.50 ± 0.71 1–2 Gray-cheeked Thrush, Catharus minimus Lafresnaye 39 7.69 3 1.67 ± 0.58 1–2 10 0.00 Swainson’s Thrush*, Catharus ustulatus Nuttall 495 9.70 48 3.38 ± 3.81 1–17 141 1.42 1 1.00 1 Hermit Thrush, Catharus guttatus Pallas 162 6.17 10 2.30 ± 1.70 1–6 44 0.00 Wood Thrush, Hylocichla mustelina Gmelin 94 1.06 1 2.00 2 4 0.00 American Robin, Turdus migratorius Linnaeus 20 0.00 15 6.67 1 2.00 2 Gray Catbird, Dumetella carolinensis Linnaeus 1022 0.49 4 1.50 ± 1.00 1–3 1394 0.00 Brown Thrasher, Toxostoma rufum Linnaeus 30 6.67 2 3.00 ± 1.41 2–4 17 0.00 Blue-winged Warbler, Vermivora pinus Linnaeus 12 8.33 0 139 1.44 1 4.00 4 Nashville Warbler, Vermivora ruficapilla Wilson 219 0.00 318 0.31 1 1.00 1 Yellow Warbler, Dendroica petechia Linnaeus 361 0.00 742 0.13 1 1.00 1 Chestnut-sided Warbler, Dendroica pensylvanica Linnaeus 337 0.59 2 1.00 ± 0.00 1 178 0.00 Magnolia Warbler, Dendroica magnolia Wilson 4023 0.32 12 1.58 ± 1.24 1–5 497 0.20 1 6.00 6–6 Black-throated Blue Warbler, Dendroica caerulescens Gmelin 538 0.00 482 0.83 4 1.50 ± 1.00 1–3 Yellow-rumped Warbler, Dendroica coronata Linnaeus 669 0.00 528 0.19 1 1.00 1 Prairie Warbler, Dendroica discolor Vieillot 6 0.00 84 1.19 1 1.00 1 Blackpoll Warbler, Dendroica striata Forster 1082 0.18 2 1.00 ± 0.00 1 642 0.00 Black-and-white Warbler, Mniotilta varia Linnaeus 1005 0.20 2 1.50 ± 0.71 1–2 746 0.54 4 2.00 ± 2.00 1–5 2007 S.R. Morris, M.C. Ertel, and M.P. Wright 175 Table 2, continued. Spring Fall Mean Mean Common name NA %B NC (± S.D.)D RangeE NA %B NC (± S.D.)D RangeE American Redstart, Setophaga ruticilla Linnaeus 2059 0.05 1 2.00 2 1780 0.51 7 2.71 ± 3.25 1–10 Worm-eating Warbler, Helmitheros vermivorus Gmelin 7 28.57 2 1.50 ± 0.71 1–2 2 0.00 Ovenbird*, Seiurus aurocapilla Linnaeus 1068 2.81 27 1.93 ± 1.36 1–5 426 4.46 16 4.19 ± 4.23 1–16 Northern Waterthrush*, Seiurus noveboracensis Gmelin 697 4.02 27 1.67 ± 0.83 1–4 2407 1.29 28 3.43 ± 4.71 1–24 Mourning Warbler, Oporornis philadelphia Wilson 247 2.83 7 3.00 ± 1.73 1–6 219 3.65 7 1.57 ± 1.51 1–5 Common Yellowthroat*, Geothlypis trichas Linnaeus 6679 7.46 483 2.03 ± 1.52 1–12 1782 1.68 28 3.07 ± 3.22 1–15 Wilson’s Warbler, Wilsonia pusilla Wilson 209 0.00 434 0.46 2 1.00 1 Canada Warbler, Wilsonia canadensis Linnaeus 886 0.56 5 1.40 ± 0.89 1–3 254 1.57 3 5.67 ± 5.03 1–11 Yellow-breasted Chat, Icteria virens Linnaeus 3 0.00 129 0.78 1 5.00 5 Scarlet Tanager, Piranga olivacea Gmelin 129 0.78 1 1.00 1 57 1.75 1 3.00 3 Eastern Towhee, Pipilo erythrophthalmus Linnaeus 43 4.65 1 7.00 ± 4.24 4–10 4 0.00 Field Sparrow, Spizella pusilla Wilson 19 10.53 2 2.50 ± 2.12 1–4 0 Savannah Sparrow, Passerculus sandwichensis Gmelin 41 2.44 1 1.00 1 1 0.00 Song Sparrow, Melospiza melodia Wilson 94 0.00 803 0.12 1 2.00 2 Lincoln’s Sparrow, Melospiza lincolnii Audubon 290 3.45 9 2.44 ± 1.74 1–5 34 0.00 Swamp Sparrow, Melospiza georgiana Latham 342 6.43 21 2.10 ± 1.48 1–6 55 0.00 White-throated Sparrow*, Zonotrichia albicollis Gmelin 1877 2.02 36 1.61 ± 1.34 1–8 577 2.08 11 9.09 ± 15.92 1–54 White-crowned Sparrow, Zonotrichia leucophrys Forster 26 3.85 1 1.00 1 5 0.00 Dark-eyed Junco, Junco hyemalis Linnaeus 9 0.00 191 2.62 4 12.25 ± 11.87 5–30 Indigo Bunting, Passerina cyanea Linnaeus 26 0.00 17 5.88 1 1.00 1 Common Grackle, Quiscalus quiscula Linnaeus 30 0.00 21 4.76 1 2.00 2 Baltimore Oriole, Icterus galbula Linnaeus 132 0.00 401 0.25 1 1.00 1 ANumber of birds examined for ticks. BPercent of examined birds parasitized by ticks. CSample sizes were often lower than the actual number of birds parasitized by ticks. During the early years of the study, the number of ticks on individual birds was not always reported. DMean number of ticks on individual birds. ERange of number of ticks on individual birds. 176 Northeastern Naturalist Vol. 14, No. 2 Results There were 57,400 birds captured and banded on Appledore Island between 1990 and 2002 (Table 1), representing a total of 134 species. Overall, 1.6% of migrants were parasitized by ticks, and these birds represented 48 species. Swainson’s Thrush (SWTH, 7.9%), Common Yellowthroat (COYE, 6.2%), Ovenbird (3.3%), White-throated Sparrow (2.0%), and Northern Waterthrush (NOWA, 1.9%) were the species most likely to have ticks (Table 2). During spring, 2.4% of migrants were parasitized by ticks, whereas only 0.6% were parasitized by ticks during fall. During spring, the average number of ticks per infested bird was 2.11 ± 1.80 (733 birds with ticks, range = 1–17 ticks per bird), while during fall, the average number of ticks on a bird was 3.77 ± 6.22 (132 birds with ticks, range = 1–54 ticks per bird). Among all species studied, we did not find a consistent pattern of increased proportion of birds parasitized by ticks or a higher number of ticks on individual birds during one season compared to the other season (Table 2). Among the five species most likely to be parasitized by ticks, Swainson’s Thrushes, Common Yellowthroats, and Northern Waterthrushes were more likely to have ticks during spring than during fall (SWTH: 􀁲2 1 = 14.1, P < 0.001; COYE: 􀁲2 1 = 103.6, P < 0.001; NOWA: 􀁲2 1 = 18.2, P < 0.001), but there were no significant differences between seasons in the average number of ticks on infested individuals. In Common Yellowthroats, the only sexually dimorphic species among the five most common tick hosts, we did not find a significant difference between males and females in the proportion parasitized by ticks during fall (􀁲2 1 = 0.0, P = 0.976) or the number of ticks on individuals in either season (spring: t459 = 0.42, P = 0.672; fall: t3 = 0.95, P = 0.411). During spring, males were significantly more likely than females to be parasitized by ticks (male: 8.8%; female: 6.2%; 􀁲2 1 = 16.5, P < 0.001). Among the five most common tick hosts, we did not find a significantly lower mass, fat, or body condition among birds parasitized by ticks compared with those without ticks (Table 3). In fact, in the only case in which we found a significant difference, Common Yellowthroats with ticks had a slightly, but significantly, higher mass than those without ticks during spring (t571.8= 3.70, P < 0.001). Furthermore, presence of ticks did not appear to impact the stopover ecology of migrants. Generally, birds parasitized by ticks did not differ in recapture rates or stopover lengths from birds without ticks (Table 4). However, among Northern Waterthrushes, individuals parasitized by ticks were more likely to be recaptured than those without ticks during spring (􀁲2 1 = 7.7, P = 0.006). In contrast, during fall, Common Yellowthroats with ticks stayed on Appledore for less time than individuals without ticks (t4.4 = 5.3, P = 0.004). 2007 S.R. Morris, M.C. Ertel, and M.P. Wright 177 Table 3. Presence of ticks on birds did not affect the condition of migrants on Appledore Island, ME. Data from 1990 to 2002 were pooled. Birds without ticks Birds parasitized by ticks Species N Mass Fat ConditionA N Mass Fat ConditionA Spring Swainson’s Thrush 443 31.48 ± 3.21 0.99 ± 0.61 32.27 ± 3.19 48 30.97 ± 3.10 0.96 ± 0.62 31.76 ± 3.14 Ovenbird 1031 19.40 ± 1.71 0.84 ± 0.60 26.49 ± 2.20 30 20.03 ± 1.52 0.87 ± 0.41 27.27 ± 1.90 Northern Waterthrush 664 17.70 ± 1.78 1.18 ± 0.78 24.08 ± 2.26 28 17.83 ± 1.70 1.29 ± 0.71 24.19 ± 2.23 Common Yellowthroat 6134 10.04 ± 0.86 0.69 ± 0.58 19.24 ± 1.45 496 10.19 ± 0.89 0.69 ± 0.57 19.36 ± 1.49 White-throated Sparrow 1828 25.10 ± 2.84 1.07 ± 0.74 36.14 ± 3.78 38 25.60 ± 1.95 1.28 ± 0.78 36.91 ± 2.83 Fall Swainson’s Thrush 139 31.36 ± 3.52 0.73 ± 0.63 32.34 ± 3.47 2 32.85 ± 1.45 1.50 ± 0.71 33.36 ± 1.95 Ovenbird 404 21.02 ± 2.79 0.96 ± 0.88 27.49 ± 3.71 19 20.89 ± 2.76 1.08 ± 0.85 29.07 ± 4.05 Northern Waterthrush 2366 17.51 ± 1.95 0.95 ± 0.69 23.75 ± 2.63 31 17.58 ± 2.26 0.87 ± 0.74 24.27 ± 3.29 Common Yellowthroat 1737 10.30 ± 0.89 0.24 ± 0.37 19.50 ± 1.58 30 9.95 ± 0.98 0.53 ± 0.52 18.88 ± 1.54 White-throated Sparrow 563 24.17 ± 2.16 0.44 ± 0.53 34.25 ± 2.66 10 24.75 ± 2.16 0.54 ± 0.62 35.22 ± 2.45 ACondition refers to mass*100/wing chord (following Winker 1995). 178 Northeastern Naturalist Vol. 14, No. 2 Discussion Previous work on Appledore demonstrated that deer ticks do parasitize migrant birds (Smith et al. 1996). The data presented here confirm the role of migrant birds as common tick hosts. Our finding that Common Yellowthroats and Northern Waterthrushes are common tick hosts on Appledore is similar to studies of migrants in coastal Georgia and Alabama (Kinsey et al. 2000). These two species and Swainson’s Thrushes also were among the species most commonly parasitized by ticks in studies of migrant birds in Canada (Morshed et al. 2005, Scott et al. 2001). Because these three species, and the other two most common tick hosts in this study, are ground foragers and/or prefer dense vegetation, it is not surprising that they were found with ticks during this study. Birds often pick up ticks from the ground in moist, forested, or shrubby habitats (Smith et al. 1996). We did find evidence of an increased proportion of migrant birds parasitized by ticks during spring compared with fall, both overall and among three of the five species most likely to host ticks. The majority of ixodid ticks that have been documented on birds in Maine are widely distributed (Keirans and Litwak 1989). Although the range of deer ticks is expanding, the species is well established in areas south of our study site, and less regularly established to the northeast of Appledore (Dennis et al. Table 4. Presence of ticks on birds did not affect the stopover ecology of migrants on Appledore Island, ME. Data from 1990 to 2002 were pooled. Birds without ticks Birds parasitized by ticks Stopover Stopover % lengthB % lengthB Species N recapturedA (days) N recapturedA (days) Spring Swainson’s Thrush 447 1.79 2.13 ± 1.25 48 2.08 1 Ovenbird 1037 8.29 2.12 ± 1.33 30 0.00 Northern Waterthrush 669 9.12 2.33 ± 2.06 28 25.00 2.43 ± 1.13 Common Yellowthroat 6180 4.45 3.37 ± 2.63 498 5.22 3.96 ± 2.63 White-throated Sparrow 1839 2.66 3.57 ± 4.56 38 0.00 Fall Swainson’s Thrush 139 8.63 1.58 ± 1.00 2 0.00 Ovenbird 406 17.24 3.64 ± 3.06 19 31.58 4.67 ± 3.67 Northern Waterthrush 2376 17.42 4.10 ± 3.28 31 22.58 4.71 ± 5.50 Common Yellowthroat 1752 16.21 6.31 ± 5.08 30 13.33 2.50 ± 1.29 White-throated Sparrow 565 4.96 5.04 ± 5.49 12 8.33 2 APercent recaptured refers to the percentage of birds that were captured at least one day after initial capture. BStopover length refers minimum stopover, which was calculated by subtracting the date of initial capture from the date of final recapture (following Cherry 1982). 2007 S.R. Morris, M.C. Ertel, and M.P. Wright 179 1998), During spring, migrants are returning from wintering grounds in the southern United States, the Caribbean, and Latin America and may be parasitized by ticks questing for hosts either on the wintering grounds or at southern stopover sites. The increased proportion of migrants parasitized by ticks during spring in this study seems to reflect the distribution of ticks and the possibility of birds bringing them north during migration. During spring, male Common Yellowthroats migrate earlier than females (Morris et al. 2003); the higher incidence of ticks on males may reflect increased tick questing early during the spring on wintering grounds or stopover sites. The higher proportion of parasitized birds needs to be interpreted with caution because it is confounded by the biology of the ticks, which were not identified to species or stage. The species and stage of the ticks will affect their expected distribution since deer tick larvae quest during the fall, while nymphs quest during the spring. However, both Demacentor variabilis larvae and nymphs may quest during the spring (Anderson 2002). Despite differences in the proportion of birds parasitized by ticks, there was not evidence of an increased number of ticks on infested individuals in either season among our most commonly captured migrant species. The low average number of ticks in our study was similar to other studies, where the mean number of ticks on parasitized birds was 2.0 on Jekyll Island, GA, 3.3 at Fort Morgan, AL (Kinsey et al. 2000), and 1.8 in Canada (Scott et al. 2001). These results may reflect the life history of ixodid ticks. The immature stages of tick species that have been documented on migrants may use birds as hosts for short (a few days) blood meals, but may not remain on birds for long periods of time (Wall and Shearer 2001). Thus, the low tick loads commonly seen on migrant birds may reflect the brief time that immature ticks spend on migrants during blood meals. Our results did not support our original hypothesis that the presence of ticks would negatively affect the body condition of migrant birds. We did not find any significant negative impact of ticks on mass, fat, or condition (mass*100/wing) of migrants. The body condition of migrant birds may not have been adversely affected because immature ticks only stay on birds for a short period of time. Except in cases of hyperinfestation, the meal size of nymphal and larval ticks may not be large enough to have detrimental effects on migrating birds. The lack of negative effects of ticks on migrant-bird condition contrasts with the results of studies on the breeding grounds, although those studies generally involved large tick loads. For example, nestling Ptychoramphus aleuticus Pallas (Cassin’s Auklets) experienced detrimental effects of severe ixodid tick infestation, including slower rates of wing growth, longer time to reach peak mass, and longer time to fledge (Morbey 1996). Post-fledging survival of Riparia riparia Linnaeus (Sand 180 Northeastern Naturalist Vol. 14, No. 2 Martins) from nests treated with pyrethrum to remove ixodid ticks was twice as high as that from the controls (Szép and Møller 2000). Additionally, breeding adult birds may also have been harmed by ticks in certain circumstances. For example, a study of breeding Aptenodytes patagonicus Miller (King Penguins) reported the death of several adults that were hyper-infested with ixodid ticks, but did not appear to have any other causes of stress (Gauthier-Clerc et al. 1998). In general, the presence of ticks did not appear to negatively affect the likelihood of recapture or stopover duration of migrants, with the exception of Northern Waterthrushes during spring. Because there was no difference in mean capture date between waterthrushes parasitized by ticks and those without ticks, this result did not appear to be a timing effect. Although Common Yellowthroats parasitized by ticks stayed for less time than those without ticks, this result should be interpreted with caution. Common Yellowthroats breed on Appledore, and the stopover length for this species may include some summer residents that were likely to stay for an extended period of time, but were unlikely to be parasitized by ticks because ticks are not indigenous to the island. The fact that only one species in one season exhibited a higher recapture rate among birds parasitized by ticks and no species exhibited longer stopovers among birds parasitized by ticks indicates that ticks are not greatly impacting stopover ecology by migrants. Acknowledgments This work was supported by student training grants from the Canisius College Biology Department and financial and logistic support from Shoals Marine Laboratory. We are very grateful to the many volunteers who assist at the Appledore Island Migration Banding Station, especially the other banders: Anthony Hill, David Holmes, John Munier, and Becky Suomala. Wayne Gall graciously assisted with discussions and provided literature on tick life-history characteristics. This paper is contribution 13 of the Appledore Island Migration Banding Station and contribution 128 of the Shoals Marine Laboratory. Literature Cited Anderson, J.F. 2002. The natural history of ticks. Medical Clinics of North America 86:205–218. 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