Harry W. Power

Egg removal and intraspecific brood parasitism in the European starling (Sturnus vulgaris).

SummaryFrom 1983 to 1986 we monitored 284 European starling (Sturnus vulgaris) nests in New Jersey for evidence of intraspecific brood parasitism and egg removal during the laying period. Egg removal occurred significantly more often at nests where intraspecific brood parasitism was detected (12 of 35 nests, 34%) than at unparasitized nests (23 of 249 nests, 9%). Brood parasitism (92% of parasitized nests) and egg removal (74% of nests with egg removal) were most common at nests where egg laying began in April of each year (i.e., early nests). Egg removal occurred at 26 (19%) and brood parasitism at 32 (23%) of 138 early nests. Both brood parasitism and egg removal were concentrated during the first four days in the laying period when brood parasitism is most likely to be successful and when host nests are most vulnerable to parasitism (Romagnano 1987). Both parasitism and removal usually involved a single egg at each nest. We detected brood parasitism and egg removal on the same day at five of 12 nests (42%) where both were observed. Because starlings do not remove foreign eggs from their nests once they begin laying (Stouffer et al. 1987) we hypothesize that parasite females sometimes removed host eggs while parasitizing nests.

Mountain Bluebirds: Experimental Evidence Against Altruism

The frequency of true altruism in nature requires assessment because, if true altruism is common, Darwins theory of natural selection is inadequate to account for all of evolution. An experiment provided birds with the opportunity to behave truly altruistically. One member of each of 25 wild pairs was collected. Ten of these were replaced naturally by courting birds, or consorts. Only one consort fostered the young of her prospective mate, and her behavior was interpretable as a reproductive error. Other consorts behaved reproductively selfishly.

Experiments on indeterminate laying in house wrens and European starlings

Although long studied, determinate and indeterminate laying patterns in birds have not been related to avian ecology. House Wrens (Troglodytes aedon) often experience egg removal by potential nest usurpers, while European Starlings (Sturnus vulgaris) commonly experience both egg removal and egg addition by conspecific brood parasites. We predicted that House Wrens should respond to egg removal by laying extra eggs but should not respond to egg addition, while European Starlings should both increase clutch size in response to removal and decrease clutch size in response to addition of eggs. We manipulated clutch size at 70 House Wren and 49 European Starling nests by adding or removing two eggs during the laying period. In early wren clutches, birds altered clutch size as predicted: wrens with nests from which eggs were removed had larger clutches than did control birds, while birds with nests to which eggs were added had clutches of the same size as control birds. However, in late clutches wrens did not respond to either egg removal or addition. Starlings showed no significant response to either egg removal or addition in spite of high rates of conspecific egg removal and brood parasitism within the study population.

Brood parasitism by starlings experimentally forced to desert their nests

Although intraspecific brood parasitism has been documented in a variety of birds (reviewed by YomTov 1980; MacWhirter 1989), in few cases have parasites been identified. Disrupted breeders, particularly females whose nests are destroyed before clutch completion, could be an important category of brood parasite in many birds (e.g. Emlen & Wrege 1986). A laying female who suddenly finds herself without a nest must find another place to lay her next egg; the ability of females to use other nests after destruction of their own may have been an important step in the evolution of interspecific brood parasitism (Hamilton & Orians 1965). Tetracycline chelates with calcium ions, which causes calcium containing tissue, including egg shells, to fluoresce under ultraviolet light. By injecting laying females with tetracycline, Haramis et al. (1983) showed that wood ducks, Aix sponsa, will sometimes lay their remaining eggs parasitically. Parasitically laid fluorescent eggs were found in nestboxes near an injected females nest. We injected European starlings, Sturnus vulgaris, with tetracycline to test the hypothesis that nest predation during egg laying can induce females to lay their remaining eggs parasitically. The study population breeds in nestboxes on the Kilmer Campus of Rutgers University in Piscataway, New Jersey. We used an intraperitoneal injection of tetracycline declomycin to label six females (Table I). We suspended powdered tablets in distilled water at a concentration of 53 mg/ml and used a dosage of 100mg/kg (Haramis et al. 1983). We caught, injected and released females on the first or second day of laying. We sealed the entrances to three nestboxes, forcing the females to desert; we did not disturb the other nests, but these females also deserted. We checked each nestbox daily and marked and weighed all new eggs until clutches were complete. During the post-laying incubation period, we photographed each clutch and examined

Pitfalls and improved techniques in avian parentage studies

-Recent studies on avian parentage have used both biochemical techniques and field observations to detect intraspecific brood parasitism and extra-pair fertilizations (EPFs). In long-term parentage studies of the European Starling (Sturnus vulgaris) using electrophoresis and field observations, we have encountered several methodological problems. Based on our findings and the existing literature, we describe these pitfalls and suggest improvements in techniques. The pitfalls include difficulty in obtaining large sample sizes, manipulation of natural populations, inaccurate allelic frequencies based on electrophoretic screening of too few individuals, catching the wrong putative parents, improper storage and handling of tissue samples, confounding effects of developmental changes in allelic expression, and misinterpretation of electrophoretic results. To improve parentage studies, we suggest censusing nest boxes around the peak times of laying to detect more than one egg per day, matching nestlings with eggs, establishing strict criteria for identifying putative parents at a nest, collecting pectoral muscle using an incision that goes in the direction of the superficial pectoral muscle fibers, and assessing the relative efficiency of laboratory and field methods to decide which would yield maximum results. Received 4 March 1988, accepted 6 September 1988. THE use of electrophoresis to study avian parentage has increased rapidly (Gowaty and Karlin 1984, Fleischer et al. 1985, Gavin and Bollinger 1985, Joste et al. 1985, Mumme et al. 1985, Evarts and Williams 1987, Westneat 1987, Wrege and Emlen 1987, Kendra et al. 1988). More recently, DNA technology has been applied to birds for the same purpose (Quinn et al. 1987, Wetton et al. 1987). The goal is to detect intraspecific brood parasitism and extra-pair fertilizations (EPFs). Intraspecific brood parasitism involves egg laying in the nest of a conspecific with no subsequent parental investment by the parasite (Yom-Tov 1980). EPFs can, but do not always have to, produce cuckoldry (Power et al. 1981). The detection of intraspecific brood parasitism or EPFs is an indication that several reproductive strategies exist in a population of birds. Comparing protein phenotypes and DNA fragment patterns between putative parent and offspring for the purpose of parental exclusion may be the only way to detect these phenomena in some cases. This is especially true of EPFs where observation (such as witnessed copulation) cannot confirm parentage. In the case of intraspecific brood parasitism, both biochemical techniques (e.g. electrophoresis and DNA fingerprinting) and field observations may be used to detect parasite eggs or offspring. The general methods of parentage studies are to collect eggs for studies of maternity only (Fleischer et al. 1985, Kendra et al. 1988) or to collect tissue (such as blood, pectoral muscle, feather pulp, or liver) from adults and nestlings for studies of maternity or paternity (Gowaty and Karlin 1984, Gavin and Bollinger 1985, Mumme et al. 1985, Evarts and Williams 1987, Quinn et al. 1987, Westneat 1987, Wetton et al. 1987, Wrege and Emlen 1987). The collected eggs or tissues are then examined for evidence of nonparentage. Field observations may be used as additional data or to supplement existing biochemical data (Quinn et al. 1987). Our purpose was to review the pitfalls of techniques used to study avian parentage and to suggest improved techniques based on our own experiences with European Starlings (Sturnus vulgaris). This review primarily pertains to field methods and electrophoresis. It is apparent from the recent literature that researchers may not be aware of all of these difficulties or the need for improved techniques. We will refer to these studies (including our own) in the spirit of constructive criticism. We feel strongly that 129 The Auk 106: 129-136. January 1989 This content downloaded from 157.55.39.243 on Thu, 06 Oct 2016 04:41:40 UTC All use subject to http://about.jstor.org/terms 130 ROMAGNANO, McGuIRE, AND POWER [Auk, Vol. 106 understanding the drawbacks of certain practices before they become common in parentage studies is important.

ON FORCES OF SELECTION IN THE EVOLUTION OF MATING TYPES

The origin, multiplication, and limitation of numbers of mating types in theoretical, primitive eucaryotic protists are considered in the context of interindividual selection. Mating types may have evolved in response to selection for outbreeding when random mating often resulted in inbreeding and individuals of different mating types were on average more genetically different than individuals of the same type. Sexual selection probably originated with mate choice in primitive eucaryotic protists. More than two mating types may persist in some populations because acceptability as a pairing partner to as many other individuals as possible may be advantageous, and/or the advantages of outbreeding may be partly countered by the advantages of adaptation to particular environments; the latter advantage is most likely to exist in a population subdivided into relatively severe but predictable habitat patches. The maximum number of mating types in a population is probably limited by selection against genetically incompatible pairings, competition between members of different mating types, and the between-sexes-choice form of sexual selection operating against genetically incompatible and/or competitively inferior individuals.

Suspected infanticide in the starling

Avian adult infanticide (the killing of conspecific young by an adult) has been reported for several species (e.g., Crook and Shields 1985, Loftin and Roberson 1983, Trail et al. 1981). Here we document one case of attempted infanticide and circumstantial evidence for 3 more cases of infanticide in the European Starling (Sturnus vulgaris). These observations were made during an ongoing study of the behavioral ecology of the starling in Piscataway, New Jersey (Power et al. 1981), from 1983 to 1985. Nest boxes were attached to utility poles found along roads and mowed fields. As part of our studies on intraspecific brood parasitism, boxes were censused daily during laying. Adults were captured after all their eggs hatched and marked with numbered U.S. Fish and Wildlife Service bands and unique combinations of color bands. On 10 May 1984, we banded the breeding female at nest box 1-18. On 11 May 1984, we banded the breeding male and again saw the banded female. This pair had three, five-day-old nestlings. Minutes after the male was banded and released at 16:30, we observed an unbanded female fly to the nest box top (starlings can be sexed from a distance by polymorphism in bill color [Bullough 1942]). She entered the nest box, looked out ofthe entrance hole several times, and then exited to the ground with something in her mouth which she attempted, but failed to eat. (We later found this object to be a fragment of an unhatched egg with dried remains of an embryo.) She then reentered the box, exited quickly, and flew out of sight at 16:40. The breeding adults at this box were not present during this time. As soon as the unmarked female left, we examined the chicks and found that one nestling had a fresh bloody wound near the auditory opening but appeared otherwise healthy; the other two nestlings were unharmed. We examined the contents of the box during the capture of the adult male at 16:30 and observed no irregularities. Therefore, we conclude that the wound was inflicted by the visiting female between 16:30 and 16:40. On 18 May 1984, at box 1-20 a twelve-day-old nestling was discovered with a wound similar to that of the chick in box 1-18, about 80 m away. This wound had to have been inflicted one or more days earlier because the eye nearest to the damaged ear was swollen and infected. Unlike the first nestling described, this nestling died. On 8 June 1983, a dead chick about five days old was found on the ground between two nest boxes, I-13 and I14, with a bad wound over its left eye. This chick was too young to have fledged or even crawled out of its nest. Moreover, no chicks were missing from any of our boxes so this chick must have been carried some distance from its nest. On 5 June 1985, we found a dead four-day-old chick at box 111-12. The area below the chicks left auditory opening was covered with blood. This chicks nestmates had already died by 4 June of apparent starvation. Their mother was banded on 3 June. A male was never captured at this box. On 6 June, an unbanded female was captured in the box and fresh nesting material was present in the nest cup. This female began laying on 12 June. In all cases, the nature of the wound was the same: a peck mark near one of the auditory openings. Similar wounds have been reported by Crook and Shields (1985), Shelley (1934), and Stacey and Edwards (1983) in the context of infanticide. The possibility that mammals or different bird species may have caused the wounds in the three cases for which we have evidence for infanticide seems remote. The only other bird that has ever been observed to enter one of our starling boxes was an American Kestrel (Falco sparverius); it was successfully repelled by the adults at that box. To discourage mammalian predators such as Raccoons (Procyon lotor) and Gray Squirrels (Sciurus carolinensis), aluminum predator guards have been placed around utility poles below nest boxes. Squirrels still occasionally present a problem. However, they always remove the entire contents of the nest (either eggs or nestlings) and disrupt the nest itself. In addition, similar peck marks have been found around the head and neck of dead adults (n = 3) found in nest boxes, and on the faces of pairs of birds that we have captured fighting inside boxes (n = 8 pairs), suggesting that bill stabbing is not uncommon. In two of the four cases, a female was suspected to have committed an infanticidal act. We suspect that infanticide in our population is related to competition for nest sites, a limiting resource (e.g., see Hrdy 1979). Other reports of female infanticidal behavior have been reported by Loftin and Roberson (1983), and Picman (1977). In both cases, a limiting resource (such as nests, mates or food) has been suggested as a reason for infanticidal acts. The importance and frequency of avian infanticide is largely unknown primarily because the observation time necessary to document this phenomenon can be prohibitive. As a result, infanticide may have greater biological significance than is implied by the existing literature. We encourage all observers to be cognizant of the possibility of infanticide in their study populations.

Repeated sampling affects Tree Swallow semen characteristics

Abstract Male Tree Swallows (Tachycineta bicolor) face intense sperm competition because mated pairs copulate frequently, extra-pair copulations are common, and females store sperm. We examined the effects of repeated sampling on the characteristics of Tree Swallow semen by manually expressing semen from 15 males immediately after capture (T0) and then hourly for 4 h (T1–T4). The semen characteristics of individual males varied in response to repeated sampling. The total number of sperm cells we obtained from each male over the 4-h sampling period varied from 104–107. Semen samples lacking sperm increased from 6.7% of T0 samples to 26.7– 33.3% of subsequent samples. Forty percent of males provided at least one semen sample that lacked sperm. There were no significant differences among hourly samples in semen volume, sperm concentration, or in the total number of sperm cells obtained from each male. However, there were significant differences among males in each of these variables. Semen volumes represented small proportions of cloacal protuberance volumes. We did not detect significant correlations between total semen volumes or total number of sperm cells obtained from males from T0–T4 and cloacal protuberance volumes. Total semen volume and number of sperm cells obtained from T0–T4 significantly increased with date. However, sperm concentration was not significantly correlated with date. We did not detect significant correlations between semen characteristics and male morphology. Individual variation in responses to repeated sampling has implications for the copulatory strategies of male and female Tree Swallows.

A model of how the sickle-cell gene produces malaria resistance.

A model of resistance to falciparum malaria provided by the sickle-cell gene in heterozygous state is presented based on earlier hypotheses, the life cycle of P. falciparum within its human host, and the nature of host response. Falciparum populations are reduced in size with each cycle of erythrocytic schizogony in sicklers because many parasitized cells are sequestered, sickled, and phagocytized within areas of low Pea following host vasoconstriction induced by antigen release during schizogony. Populations highly synchronous in their timing of schizogony grow more rapidly than asynchronous populations because a smaller proportion of their members will be trapped, sickled, and phagocytized following vasoconstriction. Differences in synchronicity of schizogony, combined with survival of early ring forms and differences between hosts in time of onset of vasoconstriction, can account for differences in the height of parasitemia between infected sicklers. The sickle-cell gene provides resistance only to falciparum malaria because other forms undergo schizogony in the peripheral circulation where PO% is too high to allow sickling, and/or their synchrony of schizogony is too great to allow a sufIicient proportion of their infecting populations to be destroyed with each cycle of erythrocytic schizogony. Resistance to falciparum malaria based upon the sickle-cell gene is restricted to early childhood because internal organs atrophy consequent to successive sickling episodes brought on by febrile diseases, including falciparum malaria itself. The gradually acquired immunity of both non-siclclers and sicklers reduces the differences in resistance between them until siclclers enjoy no advantage in falciparum resistance. Ways of testing the model are considered.

Genetic Parasitism in the European Starling

Genetic parasitism in birds has two components, cuckoldry and conspecific brood parasitism (GBP). Genetic parasitism is important because it negatively affects the reproductive success of hosts and implies the existence of more than one reproductive strategy, i.e., an individual may provide parental investment to some offspring while leaving others to be raised by conspecifics. Trivers (1972) called this a “mixed reproductive strategy.”