Shoemaker’s Ridge Road Tree Farm
1128 County Road 1500E, Urbana, Illinois 493-3571
Open Thursday through Sunday, 8 am to 5 pm and til 8 pm on Fridays
Be sure you get a fresh tree--cut it yourself!
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Shoemaker’s Ridge Road Tree Farm 1128 County Road 1500E, Urbana, Illinois 493-3571 Open Thursday through Sunday, 8 am to 5 pm and til 8 pm on Fridays Be sure you get a fresh tree--cut it yourself!
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Members, and Past President of Illinois Also members of the National Christmas Tree Association
and the Mid-America Christmas Tree Association.
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University Research on the Farm
During the past four summers, several University of Illinois graduate students have conducted research projects on our farm. All have been investigating the many birds nesting in our trees. Dylan Maddox compiled a listing of all the species of birds he saw in
our field in the summer (this was in his spare time--see below for more on
his real research). The list includes a total of 26 different types.
The asterisk denotes birds which were also found to be breeding in our tree farm. American Bittern One research project studied the growth patterns of baby grackles, and another, the parenting characteristics of robins. New in 2005 was Emily Wheeler's research on sparrows and microbial effects. Dylan kept track of each grackle nest and finally admitted to being overwhelmed when the number of nests exceeded 200! Karen actively monitored some 30 mother and father robins and their nests and counted over 150 of them in total. And, of course, numerous other species of birds have been observed nesting in our trees, too. So the chances are rather high your Christmas tree has provided a home for at least one family of young birds! It's interesting to me how quickly large numbers of birds have decided to build nests here. The field where our trees are now growing was planted to corn and soybeans prior to 1994. And it wasn't until about 1999 that the first planting of our Christmas trees were large enough that any bird would even consider using them for a nesting site. So in only 3 or 4 years, we went from zero nests to hundreds!
**************************************************************************** Here's a summary of Emily's research: Summer 2005 Pilot Studies on The Microbial Ecology and
Immune Function of Wild bird Eggs Projects generously funded by
the Geraldine R. Dodge Foundation Name: Emily
Wheeler Project
Title: Nest microbial ecology and the
effect of microbes on wild bird reproduction
Program in Ecology and Evolutionary Biology,
E-Mail:
erwheele@uiuc.edu ABSTRACT: While the effect of microbes
on reproduction in domestic poultry is relatively well described, such
information is less complete for wild species. Increased knowledge of nest
microbial ecology for wild species could be beneficial for understanding the
effect of pathogens and commensal organisms on chick development and growth, as
well as possibly providing insight about differences in immune system function
among different species in different environments. I plan to sample microbial
communities of four common species in INTRODUCTION: Recent public and wildlife health concerns include several avian-associated diseases such as West Nile Virus (WNV) and avian mycoplasmal conjunctivitis (Fischer et al., 1997; Komar et al., 2001) Diseases like WNV have demonstrated that there is a great deal of species-dependent variation in susceptibility to a particular disease (Komar et al., 2003). Emergent diseases emphasize the complexity of infectious diseases and have revealed how little is truly known about immune system function and host-pathogen interactions in wild species. Incomplete knowledge certainly compounds the difficulties faced when trying to protect humans, livestock and wildlife from the next emergent pathogen. Until
recently, the importance of pathogens for the evolution and ecology of wild
birds has been relatively ignored. In hindsight, this neglect is a bit
surprising given the many documented effects of parasites and pathogens on host
mortality and reproductive success (Scott, 1988). For example, avian malaria
epidemics are common in birds and infection is often fatal in many species.
However, even when malaria infection is not immediately fatal, it can result in
reduced reproductive success. (Oppliger, Christie and Richner 1996, 1997). Avian
malaria is a primary conservation concern in Although the number and diversity of studies on the contribution of pathogens to patterns in avian ecology have increased, there are many areas of this topic that are still relatively unexplored. One topic that still requires exploration is the effect of pathogenic and commensal microbes on avian egg composition and chick development and growth (Baggott and Graeme-Cook, 2002). I am interested in learning about the microbes to which eggs and chicks are exposed and how these communities may differ due to species or seasonal differences. I am also interested in how these communities might drive evolution of differential investment in defense against microbial invasion of the egg. Immune defenses of the egg are not only important for protecting the egg from spoilage or pathogen contamination, but may also act to modify microbial communities to which the developing chick and hatchling are exposed (Baggott and Graeme-Cook, 2002). Establishment of proper commensal flora early in life is known to serve an important role in protecting the chicks from infection with pathogenic organisms (Baggott and Graeme-Cook, 2002). Further, studies of humans and mice suggest that appropriate microbe exposure during early development plays a critical role in proper immune system maturation (Cebra, 1999; Matricardi, 2004). For these reasons, increased familiarity with nest and egg microbial ecology will enlighten investigations of immune system development and function in wild birds. In turn, a greater understanding of differences in immune system function will benefit understanding of disease susceptibility and transmission in different environments and species. While little is known about the role of microbes in wild bird reproduction, the poultry industry has long recognized the adverse effects of microbial contamination on food-safety, hatchability of eggs, and chick health. Research on domestic poultry reveals that the egg has many layers of physical and chemical defenses to microbial invasion and that the interior of a newly laid egg is usually free of microorganisms. Yet pathogenic and non-pathogenic microbes still often invade the egg after laying (Bruce and Drysdale, 1994). Microbial contamination of the egg can result in decreased hatchability or result in post-hatch morbidity or mortality. Bacteria such as Salmonella enterica, Mycobacterium tuberculosis and Mycoplasma gallisepticum, all of which cause disease in domestic poultry (as reviewed in Barrow, 1994; Cox, Berrang and Cason, 2000) can be transmitted through eggs, either via transovarian or trans-shell infection. Infection of even a few eggs in a commercial hatchery can result in rapid dissemination of disease to the rest of the hatch through horizontal contact-transmission (Mays and Takerballi, 1983; Bruce and Drysdale, 1994; Romanoff and Romanoff, 1949). The three main factors that contribute to trans-shell infection of poultry eggs are water on the egg surface, contamination of the egg surface or nest, and a temperature differential between the environment and the egg (reviewed in Mays and Takerballi, 1983; Bruce and Drysdale, 1994; Baggott and Graeme-Cook, 2002). All of these factors are very likely to affect naturally incubated avian eggs that are exposed to a wide range of weather and temperature conditions and are likely to repeatedly encounter fecal contamination within the nest. As has been demonstrated in poultry, it has been proposed that microbes in the nest are an important factor in reproductive success and hatchling health in wild birds (Baggott and Graeme-Cook, 2002; Cook et al., 2003). For wild species, however, there is very limited knowledge of nest and egg microbial ecology (Baggott and Graeme-Cook, 2002). Finally, for poultry, there is evidence that bacterial counts on the egg surface increase during warm weather. It is proposed that higher ambient temperature and humidity may increase bacterial growth and susceptibility of poultry eggs to infection (Romanoff and Romanoff, 1949). This implies that there may be significant differences in microbes within the nest and the effect of microbes on chick development for eggs laid early and late in the breeding season or in vastly different environments. MATERIALS
AND METHODS: The
objective of my project will be to investigate seasonal and species differences
in avian egg microbial ecology. To meet this objective, I will sample and
characterize microbial communities in wild bird nests in central Study
Sites: My
study will take place in Phillip’s Tract and Microbial
Ecology Survey The
first component of my project will be a survey of egg microbiology for four
common species (House Wrens, Troglodytes
aedon; House Sparrows, Passer
domesticus; American Robin, Turdus
migratorius; and Mourning Dove, Zenaida
macroura). I will evaluate changes in diversity of the microbial communities
during nesting by culturing the surface of eggs within 24 hours of laying, 24
hours after incubation has begun, and 1-2 days pre-hatching. I will also attempt
to sample the brood patches and cloacas of incubating parents at least once
during incubation when capture is possible. I will locate and sample nests from
March to August, which in central I will collect non-destructive data from all eggs in a clutch by marking eggs according to lay-order and weighing and measuring dimensions of each egg. I will remove a single egg per nest within twenty-four hours of laying so that I can sample internal contents of the egg for microbes. These eggs will be broken down into components (shell, albumen and yolk), each component sampled for microbes, and the components placed in storage at -20 degrees Celsius for possible future analysis of nutrient and immune content. The date of initiation of incubation of the eggs left in the nest will be noted and the nests will be monitored over the course of incubation. Hatch order of the eggs will be recorded and chicks will be weighed, measured, evaluated for health status, and one chick per nest will be swabbed (oral and cloacal) for comparison to microbes on the egg surface. Any egg that does not hatch within 3 days of the final successfully-hatched egg of the clutch will be necropsied and cultured to determine the stage of development and cause of hatch failure, when possible. Trans-shell
Infection Experiment: The
second component of my project will be an experiment to evaluate differences in
risk of microbial contamination of the internal components of the egg throughout
the breeding season. A recent study by Cook et al. (2003) experimentally tested
the hypothesis that increased humidity and temperature of the ambient
environment increases the potential for trans-shell migration of microbes. They
performed their study by placing domestic chicken eggs in artificial nests
exposed to ambient conditions at high and low altitude sites in If differences in risk of microbial infection are detectable between seasons within a single location, then these differences in microbial ecology should be even more pronounced in consistently different climates, such as tropical versus temperate areas. Ornithologists have long been interested in better understanding how environmental differences, particularly between tropical and temperate habitats, drive the evolution of divergent life-history strategies. There are suggestions that tropical and temperate birds differ considerably in their immunological responses to diseases (Martin et al., 2004). Investigation of differences in egg microbiology and immunological function within this context allows for a “natural” experiment on the effect of temperature and humidity on egg microbiology in wild species. Such a study not only allows for evaluation of the evolutionary response of birds to different microbial selection pressures, but also has great potential for contributing to the on-going quest to understand how environment shapes life-history strategies in tropical and temperate birds. The project I propose to perform for this fellowship will allow me to develop the skills in microbial sampling necessary to tackle this more difficult question in future field seasons. IMPORTANCE
OF FINDINGS Data obtained in this study will address a relatively unexplored component of life-history evolution – that of microbial diversity of wild bird eggs (Baggott and Graeme-Cook, 2002). These data will be collected in parallel with an on-going study which is investigating a variety of physiological and demographic patterns in life history evolution of tropical and temperate birds. My focal species are all intensively sampled as part of this study. This will provide opportunity for correlative analyses of my data with physiological and immunological information from adults of the same species. My data, both independently and in conjunction with my advisor’s (J. Brawn) project on life-history traits of avian species may reveal new insights about avian reproduction and immune system development. Secondly, this study will investigate seasonal differences in potential for trans-shell disease transmission in wild birds. Findings in the poultry literature indicate that microbial contamination can result in decreased hatchability or disease transmission from mother to chick of problematic diseases. Mycoplasmal conjunctivitis, a disease demonstrated to infect eggs by trans-shell migration in chickens (Barrow, 1994), has recently moved from domestic poultry to wild birds and has become an important disease of conservation concern (Fischer et al., 1997). Diseases that can be transmitted between domestic and wild birds are especially concerning due to the high mobility of wild species; avian dispersal and migration are suspected to have caused the surprisingly rapid spread of emergent diseases like mycoplasmal conjunctivitis and WNV (Fischer et al., 1997; Rappole, Derrickson and Hubalek, 2000; Townsend, Vieglais and Andreasen, 2003). For this reason, it is imperative that researchers develop a better understanding of the potential routes of transmission for zoonotic diseases; trans-shell and transovarian transmission are an established route of disease propagation in domestic poultry that have not been investigated thoroughly in wildlife. Finally, recent studies in mammalian immunity suggest that disease exposure during early development of the immune system plays an important role in shaping proper immune system function (Cebra, 1999; Matricardi, 2004). By evaluating changes in the microbial community of the nest over the course of development through hatching I will provide information on the types of microbes the chick is exposed to during immune system development. A better understanding of early microbial exposure experienced by avian species may be important for better understanding of immune system development and function. With rising concerns about environmental change and the effects of these changes on the movement of pathogens, it is more important than ever to increase our understanding not only of pathogen transmission dynamics, but also the effect of pathogens on fitness and evolution of wild species. In a rapidly changing world, such information may aid prediction of how climate change and environmental degradation will effect avian populations in the future. ******************************************************************** Here's a summary of Dylan's research: Asynchronous Hatching and Brood Reduction in the Common Grackle
Dylan Maddox This hatching asynchrony provides older nestlings with a considerable size
and strength advantage because parents usually feed the larger (oldest)
nestlings first and the smaller (younger) nestlings only receive food after the
larger nestlings are replete. It is commonly believed that when food is
abundant, all nestlings receive ample amounts of food and the younger nestlings
normally survive. In years when food is scarce, however, younger nestlings
usually die from starvation (called brood reduction). In these years, it
has been suggested that brood reduction is advantageous because it is better to
have fewer well-fed nestlings than more underfed nestlings.
************************************************************************** Here's a summary of Karen's research: Parental Care and Parentage in American Robins
Despite this monogamous relationship in robins, many birds (primarily males, but females too) engage in extra-pair copulations, in which they seek to mate with individuals outside of this pair bond. These matings will often produce extra-pair young within a given nest. As individuals are trying to maximize their number of offspring in the next generation, extra-pair copulations can be advantageous particularly for males because individuals are increasing the number of their own offspring in the next generation without actually helping to raise them because they are in the nest of, and being raised by, another individual. While this strategy may seem beneficial to the male seeking extra-pair copulations, the male who was cuckolded will lose parentage in his own nest; that is, the number of offspring carrying his genes will go down. As such, many males will engage in strategies that "protect their parentage" in which males stay very close to their social mates during the time in which their female is fertilizable. The only problem with this strategy for robins comes in when pairs begin a second nesting attempt. To increase the number of clutches a pair can produce in a season, robins can decrease the amount of time between each nesting attempt. Although offspring leave the nest at about 14 days post-hatch (called fledging), they still require about 2 weeks of constant care before they become independent. Since males cannot lay eggs to begin the next nesting attempt, males will take over caring for the offspring that have fledged, allowing the female to begin the next nesting attempt sooner than if they both continued to care for the young until they were independent. And as the male becomes preoccupied with caring for those fledglings, he is unable to protect his parentage with his social mate. She has every opportunity to seek out extra-pair copulations with other males because her mate is preoccupied with caring for their young from the first nest. But research has shown that many females do not seek to mate outside of their pair bond at the second nests, despite the fact that they may benefit from doing so. Why they do not is the focus of my dissertation research. Because male care is important for the survival of offspring, females may be faithful to their mates in second nests (despite their opportunity to seek extra-pair copulations), to ensure that their mates will care for offspring in second nests as well. Males who have a decreased certainty of parentage (such as in cases where they were unable to guard their mates) should be less likely to care for those offspring because those who preferentially care for their own offspring are favored through natural selection over those that do not. Therefore, when males are good providers to their offspring (which the female can assess during the first nesting attempt), females will be less likely to seek extra-pair copulations at second nests to assure that her partner will provide good care to the second nest offspring as well. My research focuses on testing this
hypothesis through both observational and experimental studies of the breeding
robins. Adult birds are individually marked by using plastic color bands,
allowing me to follow pairs throughout the season. I assess parental care
by videotaping adults feeding their young at the nest and observing the
defensive behavior of the adults whenever I approach the nest. I also
gather blood samples from adults and nestlings to determine parentage.
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