Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 243-268). Available also in a digital version from Dissertation Abstracts.

Thesis (M.S. - Renewable Natural Resources) - University of Arizona. / Includes bibliographical references (leaves 135-148).

Thesis (Ph.D.) -- McMaster University, 2000. / Includes bibliographical references. Also available via World Wide Web.

Thesis (Ph.D.) -- McMaster University, 2000. / Includes bibliographical references. Also available via World Wide Web.

<p> The mtDNA control region of the Brown-headed Cowbird (Molothrus ater) was sequenced and comparisons made at the inter- and intraspecific level. Comparison of the control region with that of another Passerine, Darwin's Finch (Geospiza scandens), revealed a high degree of both gross and fine scale structural similarity. At the nucleotide level, this comparison confirmed the presence of a hypervariable domain which evolves at rate approximately 5 times faster than coding mtDNA as well as a relatively conserved central domain which evolves at rate comparable to coding mtDNA. Both species displayed the typical avian mtDNA gene organisation previously described by Desjardins and Morais (1990, 1991) and Quinn and Wilson (in press). However, the most notable structural feature in common was the apparent deletion of the entire left hypervariable domain (CR1). At a finer scale, Conserved Sequence Block (CSB1) was perfectly conserved between cowbird and finch and Conserved Sequence Block 2 (CSB2) was 78% similar. The hypervariable right domain showed the largest degree of sequence divergence between species, 22.7%, while the central domain and phe-tRNA showed much less divergence, 6.47 and 4.41% respectively. At an intraspecific level, in 524 bases of sequence from 31 nestling cowbirds from a population at Delta, Manitoba, only 3 variable sites were detected which defined a total of 4 haplotypes. The average percent sequence divergence for this population was 0.27%. This level of variation within the cowbird population is low compared to other vertebrate populations. This relative lack of variation is largely attributable to the loss of the left hypervariable domain (CR1). The loss of CR1 will limit the control region's usefulness for high resolution population level studies but may make it a useful marker for phylogenetic studies within the class Aves.</p> / Thesis / Master of Science (MSc)

Doctor of Philosophy / Department of Biology / Brett K. Sandercock / The reproductive strategies of avian brood parasites and the behavioral responses of their hosts have served as a model of co-evolution in nature. Host adaptations to reduce the costs of parasitism are countered with novel parasite behaviors that increase the success of the parasite and thereby decrease host productivity. Not all host species possess anti-parasite defense behaviors, and parasitism by Brown-headed Cowbirds (Molothrus ater) may cause population declines in some species. Bell’s Vireo (Vireo bellii) is a small-bodied cowbird host that fails to fledge young if successfully parasitized. Although vireos desert naturally parasitized nests, the cues that cause desertion have not been identified. Understanding how parasitism affects vireo productivity is important because cowbird removal is an integral component of the recovery efforts for the endangered Least Bell’s Vireo (V. b. pusillus) in California. However, it is generally unknown how cowbird removal affects vireo productivity. To address these issues, I monitored the productivity of vireos nesting in Kansas at the Konza Prairie Biological Station, conducted a clutch manipulation experiment, and experimentally removed cowbirds. In addition, I used stable isotope analysis to determine if recently fledged cowbird young could be assigned to habitats or host species. I found that vireos did not desert nests due to the presence of a cowbird egg; rather egg removal by cowbirds caused desertion, which is a generalized response in many taxa of birds. Cowbird removals decreased parasitism of vireo nests by approximately 36% and led to a 2-fold increase in vireo productivity per pair. Cowbird productivity from vireo pairs increased because fewer parasitized nests were deserted and parasitized nests on removal plots had a higher probability of success. No cowbird removal study has reported an increase in cowbird productivity in response to trapping. Cowbird nestlings from prairie plots and shrub plots differed in carbon and nitrogen isotope compositions, and 87% of locally produced juvenile cowbirds were classified with nestlings from shrub plots. Thus, the continued expansion of woody plants into tallgrass prairie may result in local increases in cowbird productivity.

Brood parasitic birds lay eggs amongst the clutches of other species, which then assume all costs of parental care on their behalf. This thesis addresses several puzzles of avian brood parasitism, using field studies and theoretical modelling of the generalist parasite, the shiny cowbird (Molothrus bonariensis) and select hosts in Argentina. Key findings and conclusions were: • High parasitism intensity in a host population can result in a cost to hosts of removing parasite eggs from their clutches, and so help to maintain host’s acceptance of parasite eggs in evolutionary equilibrium. The cost is to host egg survival: hosts that remove parasite eggs from the clutch increase the risk that their eggs are destroyed by subsequent parasites that visit the nest. • The principal benefit of mobbing as a front-line defence of hosts may be to reduce egg loss due to parasite attack, rather than prevent parasitism itself. • Differences in the acoustic structure of begging calls between parasites and their host’s young can be to the parasite’s advantage. Parents provisioned unparasitized broods more during broadcast at the nest of shiny cowbird calls than calls of their own species’ chicks, in both a common host and a non-host. The long tremulous quality of a cowbird’s call functions analogously to a rapid call rate, thereby exploiting a common provisioning rule of avian parents. • A trade-off for maximum growth in parasite nestlings will variously favour or not favour the evolution of nestmate-killing behaviour, depending on a parasite’s abilities, relative to host young, to solicit and attain provisions from host parents. Generalist parasites can encounter both sides of the trade-off in different hosts. Meanwhile, indirect fitness costs are unlikely to constrain the evolution of nestmate-killing in shiny cowbirds, as they rarely, if ever, share the nest with siblings.

Obligate brood parasites rely solely on other species, the hosts, to incubate their eggs and raise their offspring, which often reduces the host’s reproductive output. This reproductive cost has led to the evolution of anti-parasite adaptations among hosts, which in turn, has led to better trickery by parasites, a process termed an evolutionary arms race. The objective of this thesis was to investigate host-parasite coevolutionary arms races to address questions of host-use diversity. Host diversity varies dramatically among brood-parasitic species, but reasons for variations in host-use among brood parasites are not well understood. In Chapter 2, I address questions on host diversity specifically, whereas I address questions about coevolutionary interaction between hosts and parasites in Chapters 3, 4 and 5 using two host-parasite systems, one in New Zealand and one in North America. Chapter 2 investigates if host diversity is constrained by aggressive nest defence behaviour. I compared the nest defence behaviour of the exclusive host of the shining cuckoo Chrysococcyx lucidus lucidus on the main islands of New Zealand, the grey warbler Gerygone igata, to two other potentially suitable hosts that are not currently parasitised, the fantail Rhipidura fuliginosa and the silvereye Zosterops lateralis. The results suggest that grey warblers are as aggressive as fantails and silvereyes towards shining cuckoos at the nest and thus, host specialisation in shining cuckoos in New Zealand, at least, does not appear to be the result of nest-defence constraints imposed by potential but unused host species. Chapter 3 investigates if red-winged blackbirds Agelaius phoeniceus, a species that typically accepts the eggs of parasites, recognises, as indicated by changes in incubation behaviour, when they have been parasitised by brown-headed cowbirds Molothrus ater. Recognition without rejection suggests that rejection may be context-dependent but the results suggest that red-winged blackbirds do not recognise when their nests have been parasitised by brown-headed cowbirds, at least at the egg stage. This study was the first to investigate if hosts that almost invariably accept the eggs of parasites recognise when they have been parasitised. Chapter 4 investigated the possibility of coevolutionary arms races occurring through olfactory channels in contrast to earlier work that focussed only on visual and auditory cues. Recent research has revealed that olfactory abilities in birds are more common than previously thought. Uropygial gland secretions are posited to be a key source of avian body odour and its composition has been found to vary among species and individuals as well as between the sexes. I compared gas-chromatography (GC-FID) traces of shining cuckoo preen wax to the GC-FID traces of the grey warbler, the only host of the shining cuckoo in mainland New Zealand, as well as the preen wax of seven other species for evidence of mimicry. Preliminary results suggest there is evidence for mimicry and the potential for odour-based nestling discrimination in grey warblers. Further tests recording the response of grey warblers to odour-manipulated nestlings are necessary. Finally, in Chapter 5, I investigated the response of the song thrush Turdus philomelos, a species that rejects the eggs of the common cuckoo Cuculus canorus and conspecifics at intermediate and low frequencies, respectively, to nest-odour manipulations using the preen wax of conspecifics and heterospecifics. The results suggest song thrush do not use odour to assess the risk of parasitism at least as indicated in terms of changes in incubation behaviour. Investigations of the role of olfaction in avian brood parasite systems can provide a better understanding of brood-parasite coevolution. Only by considering all channels of communication can we be sure to completely understand the coevolutionary dynamics between brood parasites and their hosts.

Master of Science / Department of Biology / Brett K. Sandercock / Grassland birds are declining throughout their native range. The Flint Hills of eastern Kansas and Oklahoma contain large tracts of tallgrass prairie, but intensification of agricultural practices may be contributing to ongoing population declines. Common rangeland management practices include annual burning coupled with heavy grazing by cattle. This system, known as intensive early stocking and burning, promotes homogeneous utilization of forage by cattle but may not provide habitat for some grassland bird species. Patch-burn grazing is an alternative management system that aims to restore heterogeneity on rangelands by recreating the fire-grazing interaction that would have historically occurred throughout the Great Plains. From 2011-2013, we examined responses of grassland birds to traditional rangeland management and patch-burn grazing by conducting vegetation surveys, line transect surveys, and nest monitoring on privately-owned pastures in Chase County and Greenwood County, Kansas. Vegetative heterogeneity was higher on patch-burned pastures, with unburned patches having higher visual obstruction and less bare ground. Densities of grassland birds differed by species and among habitat strata. Unburned patches on patch-burned pastures were associated with increased densities of Dickcissels (Spiza americana), Eastern Meadowlarks (Sturnella magna) and Grasshopper Sparrows (Ammodramus savannarum). Henslow’s Sparrows (A. henslowii) were only detected on patch-burned pastures. Nest survival of grassland songbirds was similar among management systems but varied by year. Probability of nest parasitism by Brown-headed Cowbirds (Molothrus ater) varied among years and between treatments for Dickcissels and Grasshopper Sparrows, with overall lower rates on burned areas and during drought years. For Dickcissels and Grasshopper Sparrows, there was a significant reduction in host clutch size between parasitized versus unparasitized nests. Overall, nest survival of grassland songbirds in managed rangelands was low. Patch-burn grazing improved rangeland conditions and provided habitat for more species of birds, but did not increase nest survival. Drought conditions in 2012 and 2013 may have influenced the results of this study, as many landowners were unable to burn as planned. Further study is needed to determine underlying factors driving variation in nest success and parasitism rates for grassland birds, particularly on private lands which make up the vast majority of remnant tallgrass prairies.

Brown-headed cowbird (Molothrus ater) parasitism on the endangered black-capped vireo (Vireo atricapilla) is a management concern. Management for black-capped vireos in east-central Texas has focused on habitat restoration through vegetation modification. Loss of productivity due to parasitism, however, may limit the potential habitat restoration in restoring black-capped vireo populations. I investigated the relationships between frequency of parasitism on black-capped and white-eyed (V. griseus) vireos and characteristics of the neighboring avian assemblage to identify avian characteristics useful for predicting expected frequency of parasitism. I located and monitored vireo nests in March–July 2006 to determine frequency of cowbird parasitism on the 2 vireo species on 6 study sites on private land in east-central Texas. I conducted 100-m-radius circular-plot point count surveys on study sites from 1 April– 31 June 2006 to identify neighboring avian assemblages. All black-capped vireo nests (n = 20) and 81% of white-eyed vireo nests (n = 27) were parasitized. Species richness, species evenness, cumulative bird abundance, and cowbird host abundance did not differ significantly among study sites. Parasitism frequency was positively correlated with the number of cowbirds detected (r2 = 0.673, P= 0.045). Parasitism frequency was negatively correlated with abundance (r2 = 0.687, P = 0.042) and proportion of (r2 = 0.692, P = 0.040) of black-and-white warblers (Mniotilta varia), known cowbird hosts. I did not find a relationship between parasitism frequency and abundance of other cowbird hosts. The relationship between black-andwhite warbler abundance and parasitism frequency may reflect an interaction between parasitism and the vegetation characteristics associated with black-and-white warblers, suggesting the need for future study of the relationships between parasitism frequency and vegetation characteristics in the study region. The frequency of parasitism I observed suggests that cowbird control may be an important management tool if management objectives in the study region continue to include recovery of black-capped vireo populations. Number of cowbirds may be a reasonable predictor of expected parasitism frequency in an area, which may be useful to land managers in selecting areas for implementation of cowbird control.