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Eggshell pigmentation is generated by 2 major pigments, biliverdin and protoporphyrin. The latter is mostly deposited in red, brown, and black egg spots and it has been hypothesized that greater expression of egg spottiness (as measured by the number, area, and coloration of spots) may act as an honest signal of female quality for males (sexual signaling hypothesis, SSH). The important assumption of the SSH is that eggshell pigmentation correlates with phenotypic and genetic components of female quality, although phenotypic quality of females may also be under environmental control. The aim of this study was to test for the associations of protoporphyrin-based egg pigmentation with both phenotypic and genetic female traits and environmental variables (microhabitat and urbanization) in a common rallid species, the Eurasian Coot (Fulica atra). We found that the total number of egg spots was positively associated with female condition (size-corrected body mass) and expression of a putative bare-part ornament (frontal shield). The same measure of spottiness negatively correlated with the level of physiological stress in females. No evidence was found for associations between egg spottiness and genetic traits in females (neutral heterozygosity and polymorphism of pathogen recognition receptors, the Major Histocompatibility Complex), but there was a linear increase in the expression of egg spottiness over the breeding season, which may suggest that it is regulated by food availability. Our study indicates that protoporphyrin-based pigmentation of eggs reflects female phenotypic traits (condition, stress, and ornament expression) in the Eurasian Coot, although it remains to be established whether it plays any signaling role and whether it is driven by sexual selection in this species.LAY SUMMARY There is equivocal support for direct associations between maternal quality and deposition of protoporphyrin pigmentation (dark spots and blotches) in avian eggshells. Research on protoporphyrin eggshell pigmentation has primarily focused on a single avian order (Passeriformes). We examined associations of protoporphyrin-based eggshell pigmentation with female phenotypic and genetic traits in a non-passerine species, the Eurasian Coot. Deposition of protoporphyrin in eggshells (total number per area of egg spots) positively correlated with female condition and expression of a putative bare-part ornament (frontal shield), while it was negatively associated with the level of physiological stress. Protoporphyrin-based eggshell pigmentation acts as a reliable signal of female phenotypic (but not genetic) traits in the Eurasian Coot. Signaling properties of protoporphyrin-based egg coloration are likely to largely differ between different evolutionary lineages of birds.

Brood size and hatching patterns in birds are widely believed to represent adaptations to food availability during the brood-rearing period. Experimental manipulations of brood size and hatching patterns have been widely employed to determine whether parents can raise larger or more synchronous broods, but concurrent manipulations of food abundance to test the supposed causal mechanism have been rare. I studied survival to fledging of 1,060 American Coot (Fulica americana) chicks from 99 broods for which brood size, hatching asynchrony, and food availability had been experimentally manipulated via inter-nest transfers of newly hatched young and provisioning of supplemental food. Survival of color-marked young was measured until 45 days posthatch using Cormack-Jolly-Seber mark—resighting models. Survival of offspring from unsupplemented broods declined linearly with experimental increases in brood size, and this decline was large enough to ameliorate any benefits to parents from larger broods. Ho...

Helminthic parasites occur at high frequencies in waterbirds, but little is known about their effects on host population dynamics. In 2004–2005, we examined the effect of helminthic parasites on fledging success of semiprecocial American Coot (Fulica americana) chicks by experimentally dosing day-old chicks with the anthelmintic drug fenbendazole (treatments) or sterile water (controls) and measuring their survival to 40 days of age using mark—resighting analyses. In 2005, we also provided anthelmintic (treatment) or plain (control) supplemental food to incubating adults to determine whether chick survival was further influenced by parasite burdens of parents. Treated offspring had approximately half as many helminthic parasites as untreated offspring, but we could not demonstrate a reduction in parasite burdens among treated adults. Chicks that received fenbendazole in 2004 had 0.510 (85% confidence interval [CI]: 0.447–0.588) cumulative survival to 40 days of age, versus 0.387 (85% CI: 0.305–0...

Food-supplementation studies on birds during egg laying have generally manipulated macronutrients and energy. Such studies have shown variable effects on egg size in American Coots (Fulica americana). We determined the relative influences of local environment, food quantity, and food quality on egg size in American Coots by supplementing food and carotenoids at three sites in Saskatchewan. Eggs were collected and analyzed for carotenoid content and stable isotopes (δ15N and δ13C) in the yolk to determine whether variation in the type of food eaten contributes to egg size. We also report on the isotopic analysis of American Coot tissues and their eggs to assess evidence of endogenous versus exogenous protein and lipid allocations to reproduction. We provide isotopic evidence that American Coots used endogenous lipid, but not protein, reserves for egg formation and that egg size is more dependent on exogenous sources of nutrients. Laying sequence was the only variable across nesting locales that h...

Kleptoparasitism of American Coots (Fulica americana) by Gadwalls (Anas strep- era) was recorded from October 1991-February 1992. We used these data to test whether frequency and rate of kleptoparasitism were related to variation in food abundance and dominance status of Gadwalls. Overall, 30% (n = 423) of Gadwalls observed were kleptopar- asitic; the relative frequency and rate of kleptoparasitism varied monthly. The proportion of individuals engaged in food stealing and the rate of kleptoparasitism were greatest for subordinate sex/pair status classes of Gadwalls. When comparing diurnal time-activity bud- gets, kleptoparasitic Gadwalls spent less time feeding (56 vs. 68%) and more time searching for food (37 vs. 24%) than did individuals not participating in kleptoparasitism. watermilfoil (Myriophyllum spicatum) was the primary food of Gadwalls and American Coots. As this aquatic macrophyte declined in abundance over the winter as a result of the effects of herbivory and natural senescence, so did numbers of coots and Gadwalls. When coot and Gadwall numbers were held constant statistically, the rate of kleptoparasitism was inversely related to milfoil cover. Food-stealing behavior of Gadwalls was influenced by social domi- nance and food abundance; it was mediated by host/parasite numbers. Results suggest that kleptoparasitism is an alternative foraging strategy used by subordinate Gadwalls that do

MUCH information on laying behavior has appeared in the literature since Phillips (1887) performed his classical experiment by removing eggs daily from a flicker's nest. Lack (1947, 1948a, 1954) suggests a variety of factors that might influence clutch size, and he believes all factors are related to the maximum number of young a pair can rear successfully. Lack's ideas are based on studies of closely related species that nest over wide geographic areas. Not all workers agree with Lack's theory on food as the mechanism for controlling clutch size. Skutch's (1949) observations on tropical nesting birds indicate that these birds rear fewer young than they can nourish. Wynne-Edwards (1962) proposes that populations are regulated by social behavior before food resources are depleted. The differences of opinion existing between workers may be attributable to different mechanisms that are effective in regulating animal populations in varying degrees under a variety of conditions (Weins, 1966). Experimental studies of clutch size have been conducted on oceanic birds that are determinate layers. Clutch size has been manipulated in Laysan (Diomedia immutabilis) and Black-footed Albatrosses (D. nigripes) by Rice and Kenyon (1962) and in North Atlantic Gannets (Sula bassana) by Nelson (1964). I know of no reports in the literature that describe responses to manipulations of clutch size of indeterminate layers after the clutch is complete and incubation has started. American Coots (Fulica americana) are indeterminate layers (Sooter, 1941) and both sexes normally incubate before the clutch is complete. The eggs hatch over a period of several days, and both sexes brood and feed the young. To gain an insight into the mechanism controlling clutch size in coots, the clutch was changed by adding or removing eggs during incubation after the clutch was complete. The manipulations of clutch size provided information on the number of eggs coots can incubate successfully and the number of young they can rear successfully.

THE pip, or first break in the eggshell by the hatching bird, is the initial phase of hatching. It furnishes the bird with a weakened point at which to begin cutting the shell and complete the hatching process. The typical pip on a chicken egg is a flatly conical area about one-third of the distance from the large end, near the widest portion of the egg. Approximately 0.2 cm in height and 1 cm in diameter, it is proscribed by cracks in the shell, and has four or five additional cracks radiating from the center. The cracks are parted to varying degrees, depending upon the force from inside the shell that caused the pip. Sometime after pipping the chick begins to rotate within the egg and, starting at the pip, to jab with the egg tooth and beak tip and cut away the shell and shell membrane almost completely around the egg. It then pushes off the loosened cap thus formed at the large end of the egg and tumbles out of the shell, terminating hatching. The Musculus complexus or "hatching muscle" is a paired structure located on the anterodorsal portion of the neck in birds, originating on several anterior cervical vertebrae and inserting on the occipital crest at the rear of the skull (Fisher, 1958; Bock and Hikida, 1968). In chickens this muscle, as well as the subcutaneous area around it, starts to swell with lymph a few days prior to hatching until it reaches its peak size at the time of pipping. It then loses the fluid in a few days and assumes the appearance of normal muscle rather than being clear or yellowish and bulbous. In the adult bird it functions to raise or elevate the head. The M. complexus is probably present in enlarged form at hatching in most birds, having been described in grebes (Fisher, 1961), ducks (Keibel, 1912; Fisher, 1966), the coot, Fulica americana (J. Fisher, 1962), Franklin's Gull, Larus pipixcan (H. Fisher, 19;62), the Bobwhite, Colinus virginianus (Johnson, 1969), chicken (Fisher, 1958, and many others), and possibly in the House Sparrow, Passer domesticus, and Red-winged Blackbird, Agelaius phoeniceus (Fisher, 1958). As the peak in fluid content of the M. complexus is concurrent with pipping, it is difficult to discount the idea that it must have some role here. Keibel (1912) was apparently the first to attribute the function of breaking the eggshell to the M. complexus, and he felt that the pip was due to a contraction of the muscle, lifting and extending the beak to force the egg tooth through the shell. Pohlman (1919: 103) believed that the muscle could not contract because of its turgid condition and that

The American Coot (Fulica americana) is extremely territorial and vigorously defends its territory against not only other coots but also a wide variety of vertebrates. The effects of this interspecific intolerance upon waterfowl production were investigated, with particular emphasis upon comparative behavior, nesting and youngrearing success of coots and ducks. The following observations concern primarily the first aspect. Nesting and young-rearing success will be discussed in a later paper. This study was financed through the Utah Cooperative Wildlife Research Unit, with the U. S. Fish and Wildlife Service, Utah Fish and Game Department, Utah State University, and the Wildlife Management Institute cooperating. Dr. Jessop B. Low assisted in the direction and supervision of the project. Observations were made at various marshes in northern Utah but primarily on Ogden Bay Refuge, one of six waterfowl management areas developed by the Utah Fish and Game Department. A detailed description and history of this important waterfowl area has been published by Nelson (1954). Most findings relate to five study areas, varying in size from 15 to 76 acres, three on Ogden Bay Refuge and two on the Bay View Club, two miles west of Westpoint in Davis