Zonotrichia Albicollis Research Articles

Behavioral phenotypes persist after gonadal steroid manipulation in white-throated sparrows

White-throated sparrows ( Zonotrichia albicollis) exhibit a behavioral polymorphism that segregates with a plumage marker. Individuals with a white stripe (WS) on the crown engage in an aggressive strategy that involves more singing, whereas individuals with a tan stripe (TS) sing less and engage in more parental care. Previous work has shown that plasma levels of gonadal steroids differ between the morphs in both sexes, suggesting a hormonal mechanism for the polymorphic behavior in this species. Here, we eliminated morph differences in plasma levels of testosterone (T) in males and estradiol (E2) in females in order to test whether morph differences in behavior would be similarly eliminated. Males and females in non-breeding condition were treated with T or E2, respectively, so that plasma levels in the treated groups were high and equal between the WS and TS morphs. We found that despite hormone treatment, WS and TS birds differed with respect to singing behavior. WS males sang more in response to song playback than did TS males, and WS females exhibited more spontaneous song than TS females. We also found that WS males gave more chip calls, which are often used in contexts of territorial aggression. Overall, these results suggest that WS birds engage in more territorial vocalization, particularly song, than do TS birds, even when T or E2 levels are experimentally equalized. This behavioral difference may therefore be driven by other factors, such as steroid metabolism, receptor expression or function, or steroid-independent neurotransmitter systems.

Estradiol modulates neural responses to song in a seasonal songbird

Social behaviors such as courtship, parenting, and aggression depend primarily on two factors: a social signal to trigger the behavior, and a hormonal milieu that facilitates or permits it. Gonadal steroids may alter the valence or perceived context of the signal so that the same pheromone, vocalization, or visual display may elicit very different responses depending on the receiver's plasma hormone level. The neural processes underlying this phenomenon, however, are not well understood. Here, we describe how hormones modulate neural responses to social signals in female white-throated sparrows listening to recordings of male song. While manipulating levels of the ovarian steroid estradiol, we mapped and quantified sound-induced expression of the immediate early gene egr-1 in nine brain regions that constitute a social behavior network in vertebrates. In most regions of interest, hearing male song induced more expression than hearing tones or silence, and this selectivity for song was seen only in birds with estradiol levels typical of the breeding season. In females with regressed ovaries and no exogenous estradiol, neural responses were selective for song over tones only in the lateral portion of the ventromedial hypothalamus, not in the rest of the network. Because the effects of hormone treatment on neural responses are not identical in each region, the overall pattern of activation across the network changes with estradiol level and thus with season and breeding context. Our results demonstrate a possible mechanism by which gonadal steroids may alter the processing of social signals and affect social decision-making.

The Chromosomal Polymorphism Linked to Variation in Social Behavior in the White-Throated Sparrow (Zonotrichia albicollis) Is a Complex Rearrangement and Suppressor of Recombination

Variation in social behavior and plumage in the white-throated sparrow (Zonotrichia albicollis) is linked to an inversion polymorphism on chromosome 2. Here we report the results of our comparative cytogenetic mapping efforts and population genetics studies focused on the genomic characterization of this balanced chromosomal polymorphism. Comparative chromosome painting and cytogenetic mapping of 15 zebra finch BAC clones to the standard (ZAL2) and alternative (ZAL2(m)) arrangements revealed that this chromosome is orthologous to chicken chromosome 3, and that at a minimum, ZAL2 and ZAL2(m) differ by a pair of included pericentric inversions that we estimate span at least 98 Mb. Population-based sequencing and genotyping of multiple loci demonstrated that ZAL2(m) suppresses recombination in the heterokaryotype and is evolving as a rare nonrecombining autosomal segment of the genome. In addition, we estimate that the first inversion within the ZAL2(m) arrangement originated 2.2+/-0.3 million years ago. Finally, while previously recognized as a genetic model for the evolution of social behavior, we found that the ZAL2/ZAL2(m) polymorphism also shares genetic and phenotypic features with the mouse t complex and we further suggest that the ZAL2/ZAL2(m) polymorphism is a heretofore unrecognized model for the early stages of sex chromosome evolution.

Thirty Years of Post-fire Succession in a Southern Boreal Forest Bird Community

Birds and vegetation were surveyed in a 9 ha plot in spring 1976 in a 73 y-old jack pine (Pinus banksiana) – black spruce (Picea mariana) forest in northeastern Minnesota. A 1368 ha wildfire burned across the area that autumn. The plot was resurveyed in 1977 and periodically through 2006. Before the fire, birds with the highest importance values were Blackburnian Warbler (Dendroica fusca), Ovenbird (Seiurus aurocapillus), Red-eyed Vireo (Vireo olivaceus) and Bay-breasted Warbler (D. castanea). Within 7 y following the fire, canopy tree cover decreased to near zero as fire-damaged trees died. Afterwards, the canopy began increasing, reaching 53% cover by 30 y. Shrub cover, 8% before the fire, peaked at over 70% two decades after fire, primarily as a result of dense jack pine and black spruce regeneration, and then decreased to 58% 30 y after fire. The total number of bird species using the area doubled the first year following the fire while the number of bird species with discernable territories decreased 40%. Thereafter, territorial species began increasing and 30 y after the fire the number exceeded the pre-fire richness by 60%. Overall, density of bird territories decreased nearly three-fold the first 3 y after the fire, but by year 30, was over 56% greater than in the pre-burn mature pine forest. Loss of canopy was related to a reduction in warbler and vireo diversity while increases in woody debris and near-ground vegetation were related to an increase in ground-brush foragers such as White-throated Sparrow (Zonotrichia albicollis) and Chipping Sparrow (Spizella passerina). Brown Creeper (Certhia americana) populations increased briefly as trees died, and for five years following fire there was an increase in woodpeckers and secondary cavity nesting species. At 7 to 10 y after fire, White-throated Sparrow, Magnolia Warbler (Dendroica magnolia), Chestnut-sided Warbler (D. pensylvanica), Nashville Warbler (Vermivora ruficapilla) and Mourning Warbler (Oporornis philadelphia) dominated. White-throated Sparrow continued to be the most important bird species through the first two decades, followed by Magnolia Warbler and Red-eyed Vireo. Thirty years after fire, the dominant birds were Nashville Warbler and Ovenbird, followed distantly by Veery (Catharus fuscescens) Swainson's Thrush (Catharus ustulatus), Least Flycatcher (Empidonax minimus) and Black-and-white Warbler (Mniotilta varia). Overall, bird species using the area after 30 y remained over 70% higher than in the mature forest before the fire.

Activity of the hypothalamic–pituitary–gonadal axis differs between behavioral phenotypes in female white-throated sparrows (Zonotrichia albicollis)

The white-throated sparrow (Zonotrichia albicollis) lends itself particularly well to investigations of neuroendocrine mechanisms of social behavior because of a behavioral polymorphism that correlates with a plumage phenotype. Roughly half of the individuals of this species exhibit a white stripe (WS) on the crown and engage in a more aggressive strategy, whereas the other half exhibit a tan stripe (TS) and assume a more parental strategy. These behavioral differences are mirrored by hormonal and neuroendocrine differences; for example, males of the WS morph have higher plasma testosterone than do TS males, and females of the TS morph have higher plasma luteinizing hormone than females of the WS morph. These differences suggest that the regulation of the hypothalamic–pituitary–gonadal (HPG) axis may differ according to morph. In this study, we compared HPG axis activity at each level by measuring (1) the number, size, and staining intensity of GnRH immunoreactive (ir) neurons; (2) plasma LH; and (3) plasma estradiol (E2) in females. We found that TS females had more GnRH-ir neurons in the septo-preoptic area of the hypothalamus than did WS females, and GnRH-ir neuronal cell bodies were larger in the WS than the TS females. There was no morph difference in the intensity of GnRH labeling. TS females had higher plasma LH, which is consistent with a previous report, and higher plasma E2. We hypothesize that the differences in GnRH-ir cell number and size are related to differences in LH and E2 secretion, and may be relevant to polymorphic social behavior.

White-throated Sparrow Response to Forest Harvesting in North-Central Alberta: Results Not So Clear-Cut?

Hannah, K. C., F. K. A. Schmiegelow, and K. E. H. Aitken. 2008. White-throated Sparrow response to forest harvesting in north-central Alberta: results not so clear-cut?. Avian Conservation and Ecology - Écologie et conservation des oiseaux 3(1): 6.http://dx.doi.org/10.5751/ACE-00238-030106

A Genotyping Assay to Determine Plumage Morph in The White-Throated Sparrow (Zonotrichia Albicollis)

Abstract In alternate plumage, the White-throated Sparrow (Zonotrichia albicollis) is polymorphic, such that individuals exhibit a median crown stripe that is either white or tan in color. This plumage polymorphism is believed to be caused by a chromosomal inversion and predicts many aspects of an individual’s aggressive and parental behavior, which makes this species an interesting and valuable subject for the study of the genetic basis of social behavior. Although the plumage polymorphism is well described, in practice the determination of morph for individual birds is not perfectly straightforward. Whereas morph can be assessed relatively easily in alternate plumage, birds in basic plumage tend to show coloration characteristic of both morphs. During the winter and fall, therefore, plumage morph cannot be determined with 100% accuracy by visual inspection alone. Here, we describe a genotyping assay that reliably predicts morph in alternate plumage. DNA from one drop of blood is amplified by PCR, digested and run on an agarose gel. The resulting banding patterns are used to distinguish white-striped from tan-striped birds with 100% accuracy. This method is fast and economical compared with karyotyping, is far less subjective than assessment of morph by plumage characteristics, and can be performed using any kind of sample from which DNA can be extracted. Un test génotypique pour déterminer la forme du plumage chez Zonotrichia albicollis

Planning timber harvest of residual forest stands without compromising bird and small mammal communities in boreal landscapes

Numerous efforts have been invested in designing and configuring residual forest stands in Canadian boreal forest to preserve their overall biodiversity. Now that several landscapes have been partially logged, the next issue in forest management involves the planning of residual forest stand harvesting without compromising wildlife populations. Residual stands can be cut when adjacent regeneration reaches 3 m in height according to current regulations in several Canadian provinces (e.g., Québec, Ontario, Alberta, and British-Columbia). However, little is known on whether such regenerating habitat (RE-3m) can maintain wildlife communities similar to those found in unharvested mature forest (CO). We estimated the relative abundance of small mammals and forest birds in RE-3m and CO habitats and characterized landscape and stand structures. These variables were then compared between the two contrasting successional stages and were used to build habitat use models (HUMs) for 21 species. CO and RE-3m differed with regard to several landscape characteristics and stand structure variables as a result of logging. Snowshoe Hare, Northern Flicker, Alder Flycatcher, Ruby-crowned Kinglet, White-throated Sparrow and Magnolia Warbler were more abundant in RE-3m than CO, while Red-backed Vole, Brown Creeper and Golden-crowned Kinglet exhibited lower abundances in RE-3m. No significant differences in abundance were observed for the 12 other species. Species HUMs were highly significant and explained between 64.3 and 99.1% of the total variability in abundance. Following variance partitioning, stand structure variables accounted for most of the explained variability (54.2%) while landscape characteristics accounted for only 28.7%. No difference in species richness was observed but community evenness was greater in CO than RE-3m. Our results suggest that current regulations may threaten the maintenance of 3 out of 21 censused species for which abundances were significantly lower in regenerating 3 m tall stands. As stand structure explained a large amount of variability in abundance, it should be considered during timber harvest planning in both mature and regenerating stands. Until we know more on whether the current regulations are suitable for maintaining overall biodiversity, our results suggest that some mature forest stands should be maintained within managed landscapes for a complete logging rotation period.

Rapid Neuroendocrine Responses to Auditory Courtship Signals

In many species, courtship signals enhance reproductive function in the receiver. How these social signals are processed by the brain, particularly how they induce an endocrine response, is not well understood. Songbirds provide an ideal model in which to study this phenomenon because of the large existing literature on both their auditory neurobiology and the control of their reproductive physiology by environmental cues. To date, all of the relevant studies on songbirds have involved measuring the effects of male vocalizations on ovarian function over a period of weeks, a time course that precludes detailed analysis of the neuroendocrine mechanisms operating during song perception. We played recordings of conspecific male song to laboratory-housed female white-throated sparrows and quantified the resulting rapid changes in LH as well as the induction of the immediate early gene Egr-1 in the GnRH system and mediobasal hypothalamus (MBH). Hearing song for 42 min induced LH release and Egr-1 expression in the MBH, but did not alter Egr-1 expression in GnRH neurons. The time course of LH release and the pattern of Egr-1 expression together suggest that song acts as a trigger to induce GnRH release in a manner resembling photostimulation. The Egr-1 response in the MBH was qualitatively distinguishable from the responses to either photostimulation or pharmacologically induced LH release but seemed to involve overlapping neuronal populations. Song-induced Egr-1 expression in the MBH was correlated with the expression in midbrain and forebrain auditory centers, further supporting a role for the MBH in processing social information.

Long‐Term Effects of Group‐Selection Timber Harvesting on Abundance of Forest Birds

Relatively few studies have examined the ecological effects of group-selection timber harvesting, and nearly all have been short-term and have lacked experimental manipulations that allow pre- and posttreatment comparisons. We have been documenting the effects of a group-selection timber harvest on bird abundance in a Maine forest for 24 years (preharvest, 1983-1987; postharvest, 1988-2006). Here we characterized the trends in bird abundance over the first 20 years of the study in the managed and control halves of the 40-ha study area. Species responses to the group-selection harvest were idiosyncratic, but in general the mature-forest bird community was retained and species dependent on early successional habitat temporarily (</=8 years) benefited. The Eastern Wood-Pewee (Contopus virens), Winter Wren (Troglodytes troglodytes), Pine Warbler (Dendroica pinus), and White-throated Sparrow (Zonotrichia albicollis) increased in abundance in the managed half of the study area following timber harvest, whereas the Veery (Catharus fuscescens) decreased. The Black-and-White Warbler (Mniotilta varia), Nashville Warbler (Vermivora ruficapilla), and Common Yellowthroat (Geothlypis trichas) responded positively to harvesting, as indicated by decreases in abundance in the control area and more protracted declines or stable abundances in the managed area. This study constitutes the longest experimental investigation to date of the effects of a group-selection harvest on birds and thus provides important information on the strength, direction, and duration of temporal changes in bird populations following forest management.

Estradiol modulates brainstem catecholaminergic cell groups and projections to the auditory forebrain in a female songbird

In songbirds, hearing conspecific song induces robust expression of the immediate early gene zenk in the auditory forebrain. This genomic response to song is well characterized in males and females of many species, and is highly selective for behaviorally relevant song. In white-throated sparrows, the selectivity of the zenk response requires breeding levels of estradiol; we previously showed that in non-breeding females with low levels of plasma estradiol, the zenk response to hearing song is no different than the response to hearing frequency-matched tones. Here, we investigated the role of brainstem catecholaminergic cells groups, which project to the forebrain, in estradiol-dependent selectivity. First, we hypothesized that estradiol treatment affects catecholaminergic innervation of the auditory forebrain as well as its possible sources in the brainstem. Immunohistochemical staining of tyrosine hydroxylase revealed that estradiol treatment significantly increased the density of catecholaminergic innervation of the auditory forebrain as well as the number of catecholaminergic cells in the locus coeruleus (A6) and the ventral tegmental area (A10), both of which are known to contain estrogen receptors in songbirds. Second, we hypothesized that during song perception, catecholaminergic cell groups of the brainstem actively participate in auditory selectivity via estrogen-dependent changes in activity. We found that hearing songs did not induce the expression of zenk, a putative marker of activity, within catecholaminergic neurons in any of the cell groups quantified. Together, our results suggest that estradiol induces changes in brainstem catecholaminergic cell groups that may play a neuromodulatory role in behavioral and auditory selectivity.

Short-Term Response of Forest Birds to Experimental Clearcut Edges

Abstract Numerous studies have addressed the potential consequences of increasing the density of edges through human activities, but most have documented responses to existing edges. Here, we monitored the response of seven forest bird species to experimentally created edges around five plots (10 ha, n = 3; 25 ha, n = 2) in the boreal mixed-wood forest of Alberta, Canada. We also mapped bird detections in six control plots (10 ha, n = 5; 25 ha, n = 1). The focal species were Least Flycatcher (Empidonax minimus), Red-eyed Vireo (Vireo olivaceus), Yellow-rumped Warbler (Dendroica coronata), Black-throated Green Warbler (D. virens), Ovenbird (Seiurus aurocapilla), Mourning Warbler (Oporornis philadelphia), and White-throated Sparrow (Zonotrichia albicollis). In the two breeding seasons following experimental clearcutting, we quantified birds' responses to edges in the absence of substantial edge-induced changes in vegetation by comparing the distribution of detections between treatment and control plots. We predicted that forest-edge specialists would be attracted to edges, forest-interior specialists would avoid them, and interior-edge generalists would show a neutral response. None of these predictions was consistently supported among plots and years, except in the Mourning Warbler. However, none of the significant responses was the opposite of predictions. We also predicted that postharvest colonization of treated plots would mainly involve forest-edge specialists, whereas most local extinctions would involve forest-interior specialists. Only the colonization of 10-ha fragments followed the predicted pattern. The relatively neutral response to forest edges we observed suggests that, in general, boreal forest birds do not respond to the edge itself or to proximate cues of edge proximity. Rather, significant responses may be delayed until edge-to-interior gradients in vegetation are established. Respuestas a Corto Plazo de las Aves de Bosque a Bordes Creados Experimentalmente por Tala Rasa

Boreal forest landbirds in relation to forest composition, structure, and landscape: implications for forest management

We examined a landbird community and its relationship to environmental variables within the boreal forest in north–central Ontario to evaluate its potential usefulness as an indicator of sustainable forest management. Our study had two components. First, we compared bird assemblages in mature forest stands inside Pukaskwa National Park (n = 17) with similar forested stands in a logged landscape (n = 18) over 3 years. We found significant separation of sites in the two treatments based on an ANOSIM (analogue of the standard univariate one-way ANOVA test) of the bird communities (R = 0.238, p &lt; 0.001). We identified four significant indicators of the park landscape (bay-breasted warbler ( Dendroica castanea (Wilson, 1810)), black-throated green warbler ( Dendroica virens (J.F. Gmelin, 1789)), ovenbird ( Seiurus aurocapillus (L., 1766)), and red-eyed vireo ( Vireo olivaceus (L., 1766))) and five indicators of the logged landscape (black-backed woodpecker ( Picoides arcticus (Swainson, 1832)), brown creeper ( Certhia americana Bonaparte, 1838), winter wren ( Troglodytes troglodytes (L., 1758)), white-throated sparrow ( Zonotrichia albicollis (J.F. Gmelin, 1789)), and yellow-bellied sapsucker ( Sphyrapicus varius (L., 1776))). Some relationships were attributable to differences in vegetation, whereas other differences were attributable to the landscape context. Second, we used generalized additive models to examine the relationship of individual species with four sets of environmental data (understorey floristics, forest structure, overstorey composition, and landscape context) using the 35 sites noted above and 18 additional mature forest sites in the logged landscape (n = 53). We found that all four types of variables were frequently included in the best model based on Akaike's information criterion (AIC) (structure in 23 models, landscape in 20 models, overstorey in 19 models, and understorey in 15 models). We discuss our results in terms of their implications to forest management and note that our ability to map habitat for forest birds is substantially compromised by the lack of good spatial estimates of environmental variables that describe bird habitat.

Intraperitoneal delivery of exogenous corticosterone via osmotic pump in a passerine bird

Selecting the most reliable method to deliver exogenous steroids remains a problem for researchers, particularly when designing experiments on small birds. We used intraperitoneal (IP) osmotic pumps to deliver exogenous corticosterone (CORT) and RU486 in captive White-throated Sparrows. Males received implants containing either a low (LD) or moderate dose (MD) of CORT, RU486 (RU), or polyethylene glycol vehicle only (V). This method provided sustained elevations in baseline CORT in both LD and MD males compared to V males, with higher CORT levels induced in MD males. Slight increases in post-implant CORT resulted in V males, but not in RU males. We observed no significant change in the condition of V males in terms of body mass, furcular fat score or food intake rates, although locomotor activity declined slightly after implantation. Taken together, our results suggest that IP pumps had little impact on the overall health of the birds. CORT levels were maintained within natural ranges for this species, suggesting that our results are biologically relevant and useful for future endocrine studies with small birds.

WEST NILE VIRUS SURVEILLANCE IN EAST BATON ROUGE PARISH, LOUISIANA

West Nile virus (WNV) was detected for the first time in Louisiana in the fall of 2001. Surveillance data collected from East Baton Rouge Parish in 2002 were examined to establish baseline data on WNV activity, to support the current design of disease surveillance programs, and to target vector control efforts in the parish. The first indications of WNV activity were from a dead Northern Cardinal collected in February and from a live male cardinal sampled on 14 March. In mosquito pools, WNV was first detected on June 11. The onset of the first human case and the first detection of WNV in sentinel chickens occurred concurrently on June 24. The number of reported human cases and minimum infection rates in mosquitoes peaked in July. WNV prevalence in wild birds increased in late August and was highest in December. WNV-positive wild birds and mosquito pools were detected an average of 31 and 59 days in advance of the onset date of reported human cases, respectively, within 5 km of the residence of a human case. Antibodies to WNV were detected in sera from 7 (Northern Cardinal, House Sparrow, Northern Mockingbird, Blue Jay, Hermit Thrush, Yellow-rumped Warbler, and White-throated Sparrow) of the 42 wild bird species tested. Wild bird serology indicated WNV activity during the winter. Out of 18 mosquito species tested, the only species found positive for WNV was Culex quinquefasciatus, a result suggesting that this species was the primary epizootic/epidemic vector.

Effect of Diet Composition on Plasma Metabolite Profiles in a Migratory Songbird

AbstractAbstractPlasma metabolites provide information about the physiological state and fuel use of birds, and have been used for predicting refueling rates of birds during migratory stopovers. However, little is known about the effect of diet on metabolite concentrations in small songbirds. We investigated the effect of dietary macronutrient composition on lipid and protein metabolites in captive White-throated Sparrows (Zonotrichia albicollis). Birds fed a high-protein, low-carbohydrate insect diet had lower plasma triglyceride concentrations and higher plasma B-hydroxybutyrate concentrations than birds fed a high-carbohydrate, low-protein grain diet during feeding. The insect-fed birds also had higher plasma uric acid concentrations than grain-fed birds and birds fed a low-protein, high-fat, and high-carbohydrate fruit diet. Diet did not significantly influence plasma concentrations of glycerol or nonesterified fatty acids. After subsequent overnight fasting, birds in all three diet groups had similar concentrations of lipid metabolites, but uric acid was marginally elevated in insect-fed birds. Given that dietary macronutrient composition affected certain plasma metabolite concentrations in sparrows, investigators should consider such diet effects when using these metabolites to estimate refueling rates of free-living migratory songbirds, particularly in species that exhibit dietary plasticity during migration.

Patterns of differential migration in white-throated sparrows evaluated with isotopic measurements of feathers

We used stable isotope techniques to investigate differential migration in the white-throated sparrow ( Zonotrichia albicollis (J.F. Gmelin, 1789)), a short-distance migrant in North America, to clarify hypotheses about patterns and consequences of migration tactics. Sparrows staging in Manitoba, Canada, exhibited sex-biased differential timing of spring arrival and latitude of wintering origin. Specifically, females arrived later and originated from more southern latitudes. Furthermore, there was a negative relationship between wintering latitude and arrival dates of individuals, although this relationship was only present during the second spring of the study, since atypical cold temperatures were associated with a pulse of late-arriving sparrows during the first spring. The negative correlation between wintering latitude and arrival date was also present within males, suggesting that the distribution of males on wintering areas could have carry-over effects to reproduction. This study demonstrates potential links between events occurring on wintering and breeding grounds of migratory songbirds.

SHORT-TERM RESPONSE OF FOREST BIRDS TO EXPERIMENTAL CLEARCUT EDGES

Numerous studies have addressed the potential consequences of increasing the density of edges through human activities, but most have documented responses to existing edges. Here, we monitored the response of seven forest bird species to experimentally created edges around five plots (10 ha, n = 3; 25 ha, n = 2) in the boreal mixed-wood forest of Alberta, Canada. We also mapped bird detections in six control plots (10 ha, n = 5; 25 ha, n = 1). The focal species were Least Flycatcher (Empidonax minimus), Red-eyed Vireo (Vireo olivaceus), Yellow-rumped Warbler (Dendroica coronata), Black-throated Green Warbler (D. virens), Ovenbird (Seiurus aurocapilla), Mourning Warbler (Oporornis philadelphia), and White-throated Sparrow (Zonotrichia albicollis). In the two breeding seasons following experimental clearcutting, we quantified birds' responses to edges in the absence of substantial edge-induced changes in vegetation by comparing the distribution of detections between treatment and control plots. We predicted that forest-edge specialists would be attracted to edges, forest-interior specialists would avoid them, and interior-edge generalists would show a neutral response. None of these predictions was consistently supported among plots and years, except in the Mourning Warbler. However, none of the significant responses was the opposite of predictions. We also predicted that postharvest colonization of treated plots would mainly involve forest-edge specialists, whereas most local extinctions would involve forest-interior specialists. Only the colonization of 10-ha fragments followed the predicted pattern. The relatively neutral response to forest edges we observed suggests that, in general, boreal forest birds do not respond to the edge itself or to proximate cues of edge proximity. Rather, significant responses may be delayed until edge-to-interior gradients in vegetation are established. Respuestas a Corto Plazo de las Aves de Bosque a Bordes Creados Experimentalmente por Tala Rasa

A GENOTYPING ASSAY TO DETERMINE PLUMAGE MORPH IN THE WHITE-THROATED SPARROW (ZONOTRICHIA ALBICOLLIS)

Abstract In alternate plumage, the White-throated Sparrow (Zonotrichia albicollis) is polymorphic, such that individuals exhibit a median crown stripe that is either white or tan in color. This plumage polymorphism is believed to be caused by a chromosomal inversion and predicts many aspects of an individual’s aggressive and parental behavior, which makes this species an interesting and valuable subject for the study of the genetic basis of social behavior. Although the plumage polymorphism is well described, in practice the determination of morph for individual birds is not perfectly straightforward. Whereas morph can be assessed relatively easily in alternate plumage, birds in basic plumage tend to show coloration characteristic of both morphs. During the winter and fall, therefore, plumage morph cannot be determined with 100% accuracy by visual inspection alone. Here, we describe a genotyping assay that reliably predicts morph in alternate plumage. DNA from one drop of blood is amplified by PCR, digest...

EFFECT OF DIET COMPOSITION ON PLASMA METABOLITE PROFILES IN A MIGRATORY SONGBIRD

Abstract ABSTRACT Plasma metabolites provide information about the physiological state and fuel use of birds, and have been used for predicting refueling rates of birds during migratory stopovers. However, little is known about the effect of diet on metabolite concentrations in small songbirds. We investigated the effect of dietary macronutrient composition on lipid and protein metabolites in captive White-throated Sparrows (Zonotrichia albicollis). Birds fed a high-protein, low-carbohydrate insect diet had lower plasma triglyceride concentrations and higher plasma B-hydroxybutyrate concentrations than birds fed a high-carbohydrate, low-protein grain diet during feeding. The insect-fed birds also had higher plasma uric acid concentrations than grain-fed birds and birds fed a low-protein, high-fat, and high-carbohydrate fruit diet. Diet did not significantly influence plasma concentrations of glycerol or nonesterified fatty acids. After subsequent overnight fasting, birds in all three diet groups had simil...