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Dissertations / Theses on the topic 'Cowbirds'

Author: Grafiati

Published: 4 June 2021

Last updated: 31 January 2023

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1

Gloag, Rosalyn Suzanne. "Brood parasitism by shiny cowbirds." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:b9a9d900-ed14-4bb0-8979-7fd782584f00.

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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.

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2

Dearborn, Donald C. "Nestling behavior of a brood parasite : food acquisition and predation risk of brown-headed cowbirds /." free to MU campus, to others for purchase, 1997. http://wwwlib.umi.com/cr/mo/fullcit?p9837723.

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3

Lichtenstein, Gabriela. "Begging behaviour and host exploitation in three species of parasitic cowbirds." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627265.

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4

Schaeff, Catherine Margaret. "Why do brown-headed cowbirds, Molothrus ater, attack eggs in host nests?" Thesis, University of Ottawa (Canada), 1989. http://hdl.handle.net/10393/5659.

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5

McMaster, Donald Glen. "An experimental investigation of strategies used by brown-headed cowbirds to optimize parental care." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq23638.pdf.

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6

Kozlovic, Daniel Raymond. "Consequences of brood parasitism by cowbirds on house finches in a new area of sympatry." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0013/NQ27981.pdf.

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7

McLaren, Celia M. "Patterns of host nest use by Brown-headed Cowbirds parasitizing Song Sparrows and Yellow Warblers." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0019/MQ53191.pdf.

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8

Staab, Cara Anne 1967. "Host and nest selection by brown-headed cowbirds within a riparian area in central Arizona." Thesis, The University of Arizona, 1995. http://hdl.handle.net/10150/278488.

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Management strategies are needed to reduce the rate at which brown-headed cowbirds (Molothrus ater) parasitize their hosts. I investigated whether vegetation management could be used to reduce parasitism by seeking differences in nest-site microhabitats of hosts in a riparian area of central Arizona. During 1993 and 1994, I quantified vegetation characteristics in 0.04 ha plots centered on 128 nests of 4 commonly parasitized species and 4 infrequently parasitized species. I compared characteristics between (1) parasitized and unparasitized nests of common hosts, and (2) nests of common and infrequent hosts. Factors associated with outcome of parasitism were vegetation volume at nest, size of nest substrate, distance from nest to visual obstruction below nest, and presence of large trees near the nest. Whether nests belonged to common hosts or infrequent hosts was best predicted by nest height. My results indicate riparian areas should be managed for large trees and numerous shrubs when the goal is to reduce parasitism.

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9

Woolfenden, Bonnie. "Demography and breeding behaviour of brown-headed cowbirds, an examination of host use, individual mating patterns and reproductive success using microsatellite DNA markers." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0035/NQ66300.pdf.

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10

Burhans, Dirk E. "Anti-brood parasite defenses and nest-site selection by forest-edge songbirds in Central Missouri /." free to MU campus, to others for purchase, 1996. http://wwwlib.umi.com/cr/mo/fullcit?p9712795.

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11

Field, Kristin L. "Effects of sex ratio on ontogeny of sexual behavior and mating competence in male guppies, poecilia reticulata." The Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=osu1091578035.

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12

Francischine, Alexandra Bartel. "Confessions of a Cowbird." FIU Digital Commons, 2002. http://digitalcommons.fiu.edu/etd/3331.

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The novel, CONFESSIONS OF A COWBIRD, offers an irreverent look at family life within America's consumer culture. When the narrator, Asta Veridian, working mother, real estate broker and Vice-President of the Women in Business Association, meets Mattie Moreau, an eccentric young man who's fighting his own war against day care, the foundations of Asta's world are shaken. Although Asta and Mattie are fierce ideological opponents, their relationship escalates to a passionate level, and along the way, crimes are committed, families fall apart, suburbia is skewered, the depths of guilt are plumbed, capitalism is critiqued, sensuality and spirituality collide and unite. Underlying the action in this tragicomic, quasi-epistolary novel is the tension between self-realization and self-sacrifice, which rises to the surface when Asta realizes she may have to destroy Mattie to save her relationship with her children.

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13

Warren, Paige Shannon. "Vocal dialects in the bronzed cowbird : a model system for testing evolutionary hypotheses /." Full text (PDF) from UMI/Dissertation Abstracts International, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p3004397.

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14

Mico, Michelle A. "Yellow warbler nests, structure, building materials and cowbird parasitism." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ32191.pdf.

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15

Grant, Naomi Dawn. "Host choice of a generalist brood parasite, the brown-headed cowbird, Molothrus ater." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ31431.pdf.

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16

Kosciuch, Karl L. "Host-parasite interactions on an experimental landscape." Diss., Manhattan, Kan. : Kansas State University, 2006. http://hdl.handle.net/2097/186.

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17

Averill, Annalaura 1967, and Annalaura 1967 Averill. "Brown-headed cowbird parasitism of neotropical migratory songbirds in riparian areas along the lower Colorado river." Thesis, The University of Arizona, 1996. http://hdl.handle.net/10150/192094.

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Populations of several riparian-obligate, neotropical migratory songbirds have declined in recent years, partly due to brood parasitism by brown-headed cowbirds (Molothrus ater). In 1994 and 1995, 1 measured parasitism rates and nesting success of 4 riparian-obligate, neotropical migrants breeding in the lower Colorado River valley. Because vegetation characteristics of nest sites may influence cowbird parasitism and host nesting success, I also measured vegetation attributes associated with nest-site selection. Parasitism rates were 40-90%, and reproductive success was significantly lower in parasitized nests. Foliage cover may influence host nest-site selection and prevent cowbird nest discovery. The patchy distribution of native tree species may have aided cowbird nest discovery by providing elevated survey perches. Saltcedar (Tamarix ramosissima) was an important understory component providing foliage cover at nests. Understanding vegetation characteristics associated with host and cowbird nest-site selection should be useful in riparian restoration projects and cowbird control.

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18

Burgham, Mark Colin John. "The impact of brood parasitism by the brown-headed cowbird on the reproductive tactics of the yellow warbler." Thesis, University of Ottawa (Canada), 1985. http://hdl.handle.net/10393/5043.

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19

Jensen, William Eric. "Spatial variation in brown-headed cowbird (Molothrus ater) abundance and brood parasitism in the Flint Hills tallgrass prairie /." Search for this dissertation online, 2003. http://wwwlib.umi.com/cr/ksu/main.

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20

Tate, Douglas Patrick. "Occurrence patterns of the brown-headed cowbird, Molothrus ater, and rates of brood parasitism in island vs. mainland habitats." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ33280.pdf.

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21

Erickson, Amy Nicole. "Responses of grassland birds to patch-burn grazing in the Flint Hills of Kansas." Thesis, Kansas State University, 2017. http://hdl.handle.net/2097/35822.

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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.

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22

Rasmussen, Justin Lee. "Investigations of evolutionary arms races and host diversity in avian brood parasite systems." Thesis, University of Canterbury. Biological Sciences, 2013. http://hdl.handle.net/10092/8959.

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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.

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23

Butcher, Jerrod Anthony. "Minimum patch size thresholds of reproductive success of songbirds." Thesis, [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2842.

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24

Estopinal, Ashley. "Effects of Migratory Habit on the Genetic Diversity of Avian Populations from the Oak Openings in Northwest Ohio." Bowling Green State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1379840178.

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25

Ellison, Kevin. "Host use by sympatric cowbirds (Molothrus aeneus and M. ater)." 2005. http://hdl.handle.net/1993/20149.

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26

Kale, Claudia. "The role of host egg color in host nest selection by the brown-headed cowbird." 1985. http://hdl.handle.net/2097/27471.

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27

Klippenstine, Dwight Russell. "Can egg mimicry by brown-headed cowbirds explain the acceptance of brood parasitism by grassland passerines?" 2005. http://hdl.handle.net/1993/18095.

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28

Webster, Elisabeth M. "Behavior of Brown-headed Cowbirds foraging with American bison and insect communities of a New Mexico shortgrass prairie." 2005. http://catalog.hathitrust.org/api/volumes/oclc/61355107.html.

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29

"Phenology and brown-headed cowbird parasitism." UNIVERSITY OF COLORADO AT BOULDER, 2010. http://pqdtopen.proquest.com/#viewpdf?dispub=1469042.

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30

Averill, Annalaura. "Brown-headed cowbird parasitism of neotropical migratory songbirds in riparian areas along the lower Colorado river." 1996. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_e9791_1996_452_sip1_w.pdf&type=application/pdf.

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31

Farrell, Shannon Leigh. "Brown-headed cowbird parasitism on endangered species: relationships with neighboring avian species." 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1389.

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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.

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32

Davis, Stephen Knight. "Cowbird parasitism, predation, and host selection in fragmented grassland of southwestern Manitoba." 2009. http://hdl.handle.net/1993/3717.

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The frequency of parasitism by Brown-headed Cowbirds (Molothrus ater) and predation on ground-nesting passerines was quantified in three fragments of grassland habitat in southwestern Manitoba. All bird species studied were parasitized by cowbirds but at different parasitism frequencies. Cowbird parasitism was higher (69% of nests examined) in the smaller (22-ha) plot compared with two 64-ha plots (17% and 20%, respectively). Of the nests parasitized in all plots, 69% were parasitized multiply with 2 to 8 eggs laid per nest. There was no difference among the plots with respect to the frequency of multiple parasitism. Western Meadowlarks were parasitized at a frequency of 44%, with an average of 3.1 cowbird eggs laid in each parasitized nest. Chestnut-collared Longspurs and Sprague's Pipits were parazitized at frequencies of 18% and 14%, respectively. Parasitized nests fledged significantly fewer young (0.95) than unparasitized (1.45) nests. Only parasitized Grashopper Sparrow nests produced significantly fewer young than did unparasitized nests. Nesting success did not differ significantly between plots but nests in the smaller plot fledged significantly fewer young per nest than the other two plots. Exposed nests were more likely to be depredated than concealed nests. Cowbirds parasitized more frequently hosts that nested at highest density on each plot but parasitism frequency did not decrease with declining density of hosts. The laying season of all hosts overlapped with the cowbirds, but late nesting longspurs and Savannah Sparrows were not parasitized. Concealed nests were more likely to be parasitized than exposed nests. Parasitism frequencies were significantly lower for nests located more than 150 m from a perch and/or 100 m from the habitat edge.

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33

Neudorf, Diane Lynne. "Nest defense in four host species of the brown-headed cowbird (Molothrus ater)." 1991. http://hdl.handle.net/1993/12130.

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34

De, Groot Krista Leigh. "Community-wide impacts of a generalist brood parasite, the brown-headed cowbird (molothrus ater)." Thesis, 1998. http://hdl.handle.net/2429/8925.

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Many ecologists have searched for species that contribute strongly to the structure and composition of communities of organisms. It is widely believed that the Brown-headed Cowbird, a generalist brood parasite, is capable of changing songbird communities. Cowbird parasitism may reduce numbers of suitable hosts, i.e., songbirds that accept cowbird eggs and raise cowbird young. In contrast, songbird species that have evolved egg ejection behaviour, nest in cavities, feed cowbird nestlings an unsuitable diet or are too big to parasitize, will generally escape the effects of cowbird parasitism. Thus, cowbirds may change the composition of entire songbird communities by depressing numbers of suitable host individuals. I tested this hypothesis using an existing cowbird removal program in the state of Michigan, USA . This removal program was designed to protect the endangered Kirtland's Warbler from high levels of cowbird parasitism, throughout its 19 200 km² breeding range. I compared songbird composition in stands of young jack pine where cowbirds had been removed for 5-11 years to Control sites 5-10 km from cowbird traps and Control sites >10 km from cowbird traps. I predicted that cowbird Removal sites would support greater songbird diversity and a greater proportion of suitable host vs. unsuitable host individuals relative to Control sites. Results from songbird point counts revealed that species diversity was very similar at cowbird Removal and Control sites but Removal sites contained 4.0 - 8.7 % more suitable hosts than Control sites. I conclude that cowbirds only weakly influence the composition of songbird communities in jack pine forests of Michigan. It remains to be shown that cowbirds affect songbird community composition more strongly in other areas, e.g., midwestern USA, where cowbirds are more abundant.

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35

Guigueno, Melanie Francoise. "Acceptance or Rejection of Cowbird Parasitism: Cues Used in Decision-Making by Yellow Warblers (Dendroica petechia)." 2010. http://hdl.handle.net/1993/3958.

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The proximate causes triggering nest abandonment are unclear for most species, including the Yellow Warbler (Dendroica petechia), which abandons nests parasitized by cowbirds (via burial or desertion). Cowbird parasitism and rejection of parasitism are costly to some hosts; therefore cues affecting their responses have important evolutionary implications. Manipulative experiments showed that experimentally adding a cowbird egg elicited similar rejection frequencies (2008: 31.8%; 2009: 26.1%) as naturally laid eggs (2008: 27.1%; 2009: 20.0%). In 2008, interaction with an egg-removing model increased the probability of abandonment and the most aggressive individuals were more likely to bury the model cowbird egg. In 2009, eggs added to nests before sunrise were rejected at a frequency (29.7%) similar to eggs added to nests after sunrise (22.9%). Warblers returning to nests after egg addition peered significantly longer at their clutch than at control nests, shuffled their bodies more frequently when on the eggs and spent more time probing eggs with their bill once settled on their parasitized clutch. Furthermore, although non-mimetic blue eggs were not abandoned significantly more frequently than cowbird eggs (blue 31.1% versus cowbird 21.4%), only blue eggs were ejected from some nests. Thus, warblers use both tactile and visual cues to detect the presence of a parasitic egg in their nest. Eggs added to nests were not rejected at a lower frequency than naturally parasitized nests, as was recorded in a previous study. It is difficult to know whether this increase in abandonment of experimental eggs is due to phenotypic plasticity, genetic changes, or other factors. Egg recognition abilities may have changed because I have shown that the warblers’ behaviour changes before versus after egg addition, whereas no changes were recorded in an earlier study. Finally, not all individuals that buried eggs for the first time in 2009 (21.4%) buried again after being re-parasitized (5.3%), when less time remained in the breeding season relative to the first parasitism event. This suggests that egg rejection and host responsiveness in warblers, and likely other avian hosts that use abandonment as a form of rejection, is affected by environmental cues which may act as genetic expressers.

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36

Rasmussen, Justin Lee. "Limits of grasp-ejection in brown-headed cowbird hosts : implications for evolutionary equilibrium and evolutionary lag." 2008. http://hdl.handle.net/1993/21255.

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37

Curson, David R. "Host community dynamics and reproductive biology of a generalist avian brood parasite, the brown-headed cowbird /." 2003. http://www.library.wisc.edu/databases/connect/dissertations.html.

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38

Goguen, Christopher B. "Brown-headed cowbird movements, habitat use, and impacts on hosts in a grazed and ungrazed landscape." 1999. http://catalog.hathitrust.org/api/volumes/oclc/43844392.html.

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39

Clotfelter, Ethan D. "Impact of brown-headed cowbird brood parasitism on red-winged blackbirds and factors influencing patterns of parasitism." 1998. http://catalog.hathitrust.org/api/volumes/oclc/40742915.html.

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40

Hill, Dorothy Phyllis. "An experimental study of nest desertion by the clay-colored sparrow (Spizella pallida) in response to cowbird parasitism." 1992. http://hdl.handle.net/1993/12146.

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41

Robinson, Amber J. "Responses of song sparrows (Melospiza melodia) to threats of cowbird parasitism in areas of sympatry and recent sympatry." 2007. http://hdl.handle.net/1993/20994.

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