共查询到20条相似文献,搜索用时 46 毫秒
1.
Kathleen E. Hunt Thomas P. Hahn John C. Wingfield 《Behavioral ecology and sociobiology》1999,45(5):360-369
In males of socially monogamous birds, plasma testosterone (T) typically declines to low levels during the parental phase.
Studies on multiple-brooded species indicate that high T may be incompatible with high-quality paternal care. The length of
the breeding season may affect the costs and benefits of high T and its effect on paternal care. We studied the effect of
experimentally elevated T on paternal care in a single-brooded species with a short breeding season, the Lapland longspur
(Calcarius lapponicus). We monitored T levels and parental behavior in 16 males with subcutaneous T implants, 14 males with empty implants, and
14 unimplanted males. We videotaped nests when nestlings were 2–3 days old and again at 4–5 days. T males with 2- to 3-day-old
young visited nests and fed young less often than control males, and the mates of the T males compensated with elevated visits
and feedings. However, when nestlings were 4–5 days old, T males visited their nests at normal rates – though feeding movements
remained below normal – and T females visited and fed at normal rates. Nestling mass and nest success were similar in both
groups. Overall, high T suppresses paternal care in Lapland longspur males. The partial improvement of paternal care when
nestlings are older, despite high T, may be related to the short 6-week breeding season of this arctic species, and the consequently
reduced benefits of sexual behavior late in the breeding season.
Received: 2 February 1998 / Accepted after revision: 2 November 1998 相似文献
2.
In a recent review, Westneat and Stewart (2003) compiled evidence that extra-pair paternity results from a three-player interaction in which sexual conflict is a potent force. Sequentially polyandrous species of birds appear to fit this idea well. Earlier breeding males may attempt to use sperm storage by females to obtain paternity in their mates subsequent clutches. Later-breeding males may consequently attempt to avoid sperm competition by preferring to pair with previously unmated females. Females may bias events one way or the other. We examined the applicability of these hypotheses by studying mating behavior and paternity in red-necked phalaropes (Phalaropus lobatus), a sex-role reversed, socially polyandrous shorebird. Male red-necked phalaropes guarded mates more strongly than other shorebirds. Males increased within-pair copulation attempts during their mates fertile period, and maintained or further increased attempts towards the end of laying, suggesting an attempt to fertilize the females next clutch; these attempts were usually thwarted by the female. Paired males sought extra-pair copulations with females about to re-enter the breeding pool. Multilocus DNA fingerprinting showed that 6% of clutches (4/63) each contained one chick sired by a male other than the incubator, producing a population rate of these events of 1.7% (n=226 chicks). Male mates had full paternity in all first clutches (n=25) and 15 of 16 monogamous replacement clutches. In contrast, 3 of 6 clutches of second males contained extra-pair young likely fathered by the females previous mate. Previously mated female phalaropes may employ counter-strategies that prevent later mating males from discriminating against them. The stability of this polyandrous system, in which males provide all parental care, ultimately may depend on females providing males with eggs containing primarily genes of the incubating male, and not a previous mate.Communicated by M. Webster 相似文献
3.
Extra-pair paternity in willow ptarmigan broods: measuring costs of polygyny to males 总被引:3,自引:0,他引:3
J. R. Freeland S. J. Hannon G. Dobush P. T. Boag 《Behavioral ecology and sociobiology》1995,36(5):349-355
Willow ptarmigan are one of only three monogamous grouse species in North America. However, in some populations between 5 and 20% of individuals pair polygynously. It has been suggested that monogamy may be maintained by the high cost of polygyny to males. We have used DNA fingerprinting to assess the actual reproductive success of both monogamous and polygynous adults. We determined whether or not the putative parents were the biological parents of the chicks from 38 broods. Of these clutches 30 were from monogamous matings, and 8 were from bigamous matings. Of the 207 chicks from monogamous matings 96% were within-pair offspring, compared to 67% of the 49 chicks from bigamous matings. All extra-pair offspring chicks resulted from extra-pair fertilizations (EPFs), and there were no instances of intraspecific nest parasitism. Mate guarding by monogamous males seems to be a highly effective method for maintaining genetic monogamy, as the only cases in which EPFs occurred were when the resident female left the territory for a few days or when a second female visited the territory. Our results support the notion that certainty of parentage may be one factor constraining willow ptarmigan males to be monogamous. 相似文献
4.
Brood sex ratio is dependent on female mating status in polygynous great reed warblers 总被引:2,自引:0,他引:2
Isao Nishiumi 《Behavioral ecology and sociobiology》1998,44(1):9-14
Females capable of adjusting the sex ratio of their offspring should be more fit than females lacking such an ability. In
polygynous birds where breeding success in males is more strongly influenced by body size and/or attractiveness than in females,
females might produce more sons when predicting good conditions or when mating with attractive males. Polygynous great reed
warbler, Acrocephalusarundinaceus, males direct most of their feeding effort to the primary (first-hatching) nest and in these nests increase their feeding
effort in relation to the brood sex ratio (proportion of sons). Therefore, with the expectation of well-nourished sons, we
would predict that females which start breeding first within harems might produce more sons than those which start breeding
later, and in anticipation of sons with good genes, that females mated to polygynous males might produce more sons than females
mated to monogamous males. I took blood samples from hatchlings and determined the sex using DNA markers. The sex ratio of
primary (monogamous and polygynous primary) broods is more male-biased (mean 0.58 males, n = 50) than that of secondary (polygynous secondary and tertiary) broods (mean 0.46, n = 25). Moreover, in the secondary broods with the largest clutch (five eggs), in which offspring are most likely to suffer
food shortage, the sex ratio was distinctively female biased (mean 0.33, n = 10). In the primary broods, sex ratio was correlated to harem size. The results suggest that great reed warbler females
modify the brood sex ratio to produce both well-nourished sons and sons with good genes, but the former effect is probably
stronger than the latter factor.
Received: 11 March 1998 / Accepted after revision: 23 May 1998 相似文献
5.
Polyandry and enhanced reproductive success in the harlequin-beetle-riding pseudoscorpion 总被引:1,自引:0,他引:1
J. A. Zeh 《Behavioral ecology and sociobiology》1997,40(2):111-118
The growing molecular evidence that females of many species mate with several males calls for a critical reassessment of
the selective forces which act to shape female mating tactics. In natural populations of the harlequin-beetle-riding pseudoscorpion,
Cordylochernes scorpioides, females are polyandrous and typically produce mixed-paternity broods. Laboratory behavioral analyses and breeding experiments
indicate that polyandry in this pseudoscorpion is an active strategy which increases female reproductive success. Females
restricted to mating with a single male experienced a higher rate of embryo failure and produced significantly fewer offspring
than either females mated to more than one male in the laboratory or females naturally inseminated in the field. Forced copulation,
insufficient sperm from a single mating, male nutrient donations and variation in inherent male genetic quality cannot explain
the greater number of nymphs hatched by polyandrous females in this study. Evidence suggests that, by mating with several
males, C. scorpioides females may exploit postcopulatory mechanisms for reducing the risk and/or cost of embryo failure resulting from fertilization
by genetically incompatible sperm.
Received: 5 May 1996 / Accepted after revision: 16 October 1996 相似文献
6.
The genetic mating system of a sex-role-reversed pipefish (Syngnathus typhle): a molecular inquiry 总被引:4,自引:0,他引:4
Adam G. Jones Gunilla Rosenqvist Anders Berglund John C. Avise 《Behavioral ecology and sociobiology》1999,46(5):357-365
In the pipefish Syngnathus typhle as in other species of Syngnathidae, developing embryos are reared on the male's ventral surface. Although much laboratory
research has been directed toward understanding sexual selection in this sex-role-reversed species, few studies have addressed
the mating behavior of S. typhle in the wild, and none has capitalized upon the power of molecular genetic assays. Here we present the first direct assessment
of the genetic mating system of S. typhle in nature. Novel microsatellite loci were cloned and characterized from this species, and employed to assay entire broods
from 30 pregnant, field-captured males. Genetic analysis of 1340 embryos revealed that 1–6 females (mean = 3.1) contributed
to each brooded clutch, the highest rate of multiple maternity yet documented in any pipefish. Evidence of multiple mating
by females was also detected. Thus, this population of S. typhle displays a polygynandrous mating system, a finding consistent with previous field and laboratory observations. Our results,
considered together with similar studies of other syngnathid species, provide preliminary support for the hypothesis that
the genetic mating system is related to the evolution of sexual dimorphism in the fish family Syngnathidae.
Received: 19 January 1999 / Received in revised form: 15 April 1999 / Accepted: 9 May 1999 相似文献
7.
Correlates of extra-pair fertilization success in hooded warblers 总被引:13,自引:0,他引:13
Bridget J. M. Stutchbury W. H. Piper D. L. Neudorf S. A. Tarof Judith M. Rhymer G. Fuller R. C. Fleischer 《Behavioral ecology and sociobiology》1997,40(2):119-126
We examined correlates of extra-pair fertilization (EPF) success in the hooded warbler (Wilsonia citrina), a species where females pursue extra-pair matings. The good genes hypothesis predicts that females choose extra-pair mates
with morphological or behavioral traits that reflect differences in male genetic quality. EPFs were common, as 35.3% (42/119)
of broods contained extra-pair young (EPY) and 26.7% (95/356) of nestlings were the result of EPFs. There was a strong skew
in male EPF success which increased the variance in annual male mating success 2–3 fold. However, male morphology did not
predict EPF success, as extra-pair males were not older or larger than the males they cuckolded. Likewise, there were no significant
correlations between the proportion of extra-pair young in a brood and male size or age. The good genes hypothesis predicts
that high-quality males will be consistently preferred as genetic mates, but the number of young sired by a male with his
social mate was not consistent from one year to the next. There was a significant negative correlation between female age
and proportion of EPY produced, which could result if older females obtain higher-quality social mates. We found no strong
evidence that females choose extra-pair mates for good genes, but females may use behavioral rather than morphological cues
to assess relative male quality.
Received: 31 May 1996 / Accepted after revision: 17 October 1996 相似文献
8.
Willow B. English Douglas Schamel Diane M. Tracy David F. Westneat David B. Lank 《Behavioral ecology and sociobiology》2014,68(12):1939-1949
Fisher’s sex ratio theory predicts that on average parents should allocate resources equally to the production of males and females. However, when the cost/benefit ratio for producing males versus females differs, the theory predicts that parents may bias production, typically through underproduction of the sex with greater variation in fitness. We tested theoretical predictions in the red-necked phalarope, a polyandrous shorebird with sex-role reversal. Since females are larger and therefore potentially more expensive to produce and may have greater variation in reproductive success, we predicted from Fisher’s hypothesis a male bias in population embryonic sex ratio, and from sex allocation theory, female biases in the clutches of females allocating more resources to reproduction. We measured eggs and chicks and sexed 535 offspring from 163 clutches laid over 6 years at two sites in Alaska. The embryonic sex ratio of 51.1 M:48.9 F did not vary from parity. Clutch sex ratio (% male) was positively correlated with clutch mean egg size, opposite to our prediction. Within clutches, however, egg size did not differ by sex. Male phalarope fitness may be more variable than previously thought, and/or differential investment in eggs may affect the within-sex fitness of males more than females. Eggs producing males were less dense than those producing females, possibly indicating they contained more yolk relative to albumen. Albumen contributes to chick structural size, while yolk supports survivorship after hatch. Sex-specific chick growth strategies may affect egg size and allocation patterns by female phalaropes and other birds. 相似文献
9.
Parental care may be costly to parents because it decreases resources allocated to self-maintenance and may thus reduce survival
and future reproductive success. An inter-sexual conflict may exist in animals with obligatory bi-parental care, such as birds
of prey, in which females incubate and brood, whereas males provision food for their families. We analysed 29 years of data
(1981–2009) from a study population of Tengmalm’s owls Aegolius funereus in western Finland to examine the occurrence and timing of brood desertion and sequential polyandry, and recorded a total
of 1,123 monogamous and 12 polyandrous females. These data were supplemented with the 29-year nationwide Finnish ringing data,
which included 11,590 monogamous and 20 polyandrous females. The 12 polyandrous females started egg-laying in their two nests
at intervals of 54–68 days (mean 60 days), thus deserting their first broods when the age of oldest young averaged 21 days.
Thirty-two polyandrous females re-mated and raised a second brood at a median distance of 4.5 km (range 1–196 km). These females
produced 79% more eggs, 93% more hatchlings and 73% more fledglings than did females that laid simultaneously but remained
monogamous. Our results show that not only males, but also females of altricial species with bi-parental care can increase
their fitness by deserting their first brood when it will be cared for by the males. Earlier studies have shown that male
owls can increase their lifetime reproductive success by simultaneous polygyny, and we suggest that an inter-sexual “tug-of-war”
over bi-parental care exists in Tengmalm’s owls. 相似文献
10.
Sperm economy and limitation in spiny lobsters 总被引:5,自引:0,他引:5
Sperm limitation, when female fertilisation success is constrained by the supply of sperm, is generally perceived to be an
uncommon feature of reproduction in species which directly transfer gametes during copulation. Male size, previous copulations,
and the balance of expected reproductive return and future mating opportunity may, however, limit the amount of sperm males
transfer to females. We used laboratory experiments where mate size could be manipulated and its consequences on spermatophore
size and clutch size determined, to show that in two genera of spiny lobsters (Crustacea: Palinuridae) male reproductive output
limits the size of clutches brooded by females. In Panulirus argus from the Florida Keys, we show that while male size affects spermatophore area, males also vary the amount of ejaculate positively
with female size. Furthermore, the area of the spermatophore has a greater influence than female size on subsequent clutch
weight. In Jasus edwardsii from New Zealand, female size, male size and mate order all affect clutch weight. In both species, clutches fertilised by
small males in the laboratory are significantly smaller than clutches fertilised by large males. These results suggest that
to ensure they receive sufficient sperm, females should either mate several times prior to oviposition, mate as early as possible
in the reproductive season, or choose large, preferably unmated males as partners and thus compete with other females for
preferred males. Sperm-limited female fecundity has the potential to limit the egg production of fished populations where
large males are typically rare.
Received: 18 May 1998 / Received in revised form: 20 November 1998 / Accepted: 30 November 1998 相似文献
11.
Corey R. Freeman-Gallant 《Behavioral ecology and sociobiology》1997,40(6):395-400
Empirical relationships between parentage and male parental care are commonly interpreted in the context of life-history
models that consider increased offspring survivorship as the only benefit of paternal effort. However, indirect benefits associated
with male care can also influence a male's response to cuckoldry: if females allocate paternity according to their prior experience
with male parental care, it may pay for males to provision extra-pair young in early broods. Here, I assess the relationship
between first-brood parentage and paternal care in a population of Savannah sparrows (Passerculussandwichensis) where a male's fertilization success in the second brood appears to be influenced by his prior parental performance. Based
on the multi-locus DNA fingerprinting of 17 first broods, male feeding effort was influenced by parentage (percent of brood
resulting from within-pair fertilizations) but not by brood size, male mating status (monogamous versus polygynous), timing
of breeding (hatching date), structural size (wing length) or condition (mass). Males provided more care to broods that contained
few within-pair young. This result supports the idea that males provision young to increase their future mating success, but
alternative hypotheses involving male quality and timing of breeding cannot be excluded.
Received: 13 August 1996 / Accepted after revision: 22 February 1997 相似文献
12.
Sperm allocation in an uncertain world 总被引:3,自引:0,他引:3
Models of optimal sperm allocation are constructed using stochastic dynamic programming techniques, yielding predictions
about sperm allocation when males mate sequentially, breeding time is finite, sperm stores are limited and females vary in
quality. The models suggest that uncertainty of future reproductive opportunities should favour withholding of sperm, so that
males tend to allocate less (for a given level of stored sperm) earlier in the breeding season. This effect is more pronounced
the greater the variance in female quality. We also show that while allocation will be influenced by mate value, it is not
necessarily optimal to allocate preferentially to high-quality females, since the benefits of a higher-quality mate may be
offset by increased risk of rejection of sperm or higher sperm competition. The relationship between mate quality and level
of allocation will depend strongly on the amount of remaining stored sperm, with males whose supplies are depleted being more
likely to favour lower-quality partners.
Received: 12 September 1997 / Accepted after revision: 28 June 1998 相似文献
13.
Ben C. Sheldon Pete Davidson Gabriella Lindgren 《Behavioral ecology and sociobiology》1999,46(3):141-148
There is increasing evidence that sexual selection may be intense even in socially monogamous birds, resulting from both
mate choice and sperm competition. We studied these two modes of sexual selection experimentally by removing paired male collared
flycatchers, Ficedula albicollis, from their mates for 2 days and investigating the factors that influenced the likelihood of a replacement male appearing
and how the removals influenced paternity. Replacement males (usually neighbouring males) appeared at 81% (n = 37) of nests where males were removed. The likelihood of this appearance was unaffected by the probable reproductive value
of the female's clutch to the replacing male. A replacement was, however, less likely when the original male had a large forehead
patch, a trait previously shown to be subject to sexual selection in this population. Experimental removal of males increased
the level of sperm competition: 74% of experimental broods were multiply sired, compared to 29% of unmanipulated broods in
a previous study. Only two factors predicted how paternity was shared between males: removed males fathered more young if
removed closer to laying, and if they had larger forehead patches. The former result is consistent with last-male sperm precedence
determining paternity, whereas the latter adds to other evidence that forehead patch size is the target of female preference
in this species. Our results suggest that females exert some control over male replacement, and also that they may influence
the fertilisation success of males by behavioural means.
Received: 15 July 1998 / Received in revised form: 16 March 1999 / Accepted: 28 March 1999 相似文献
14.
Carola Borries 《Behavioral ecology and sociobiology》1997,41(3):139-150
In the seasonally breeding langur (Presbytis entellus) population of Ramnagar, South Nepal, where multimale groups prevail, 25 attacks on 11 infants (including one actual killing)
by seven adult males were witnessed in five groups by six observers between 1990 and 1996. Circumstantial evidence also indicates
three additional attempts at infanticide and in seven additional cases infanticide was presumed or likely. Infanticide presumably
accounted for 30.8–62.5% of infant mortality in the first 2 years of life. Most attackers (91.4%) were residents of the infants'
group and had immigrated after the infants had been born (75.0%) or conceived (25.0%). Thus, they were not related to the
victims. The interbirth interval was shortened if an infant died either prior to September of its 1st year of life (mean = 1.2
years), or its 2nd year (mean = 2.0) and even its 3rd year (mean = 2.4). All attackers remained in the group at least until
the next mating season; high-ranking males maintained their dominance rank and lower-ranking males rose in rank. Since rank
and mating success were correlated and rank and reproductive success might be correlated, all attackers had a good chance
of siring the next infant of the victims' mothers and could thus have benefited by their action. Infanticide seems to be a
male reproductive strategy at Ramnagar. Infanticide has never before been reported among seasonally breeding langurs living
at such low densities. This is also the first detailed report of infanticide as a male reproductive strategy in a seasonally
breeding primate population.
Received: 19 December 1996 / Accepted after revision: 7 June 1997 相似文献
15.
All other things being equal, the lifetime reproductive success (LRS) of iteroparous and semelparous individuals should scale
with the number of breeding seasons. Deviations from this relationship may occur for many reasons, including age- or size-related
fecundity or life history trade-offs, which may differ between sexes. We used 19 brood years of DNA parentage analysis in
a small (N = 4–143 year−1) wild, unexploited population of steelhead trout (Oncorhynchus mykiss) to compare the LRS of individuals that spawned only once [“one time spawners” (OTS), N = 355 male, 371 female] to those spawning twice [“repeat spawners” (RPS), N = 13 male, 49 female]. Female RPS had nearly twice the LRS of female OTS (1.17 offspring per female vs 0.91 offspring per
female), whereas male RPS had nearly three times the LRS of male OTS (1.54 offspring per male vs 0.57 offspring per male).
Female RPS produced slightly more adult offspring during their second breeding season than their first (0.78 vs 0.82 offspring
per female); however, male RPS produced all of their adult offspring in their second breeding season (0 vs 1.54 offspring
per male). The additional growth in body size of males between breeding seasons may give them an advantage in their second
breeding season, but the lack of offspring produced in their first season suggests a trade-off between survival and future
reproduction that was not expressed in females. 相似文献
16.
Costs and benefits of brood desertion in female kentish plovers,Charadrius alexandrinus 总被引:3,自引:0,他引:3
Female kentish plovers Charadrius alexandrinus typically desert their broods after the chicks hatch, i.e. 1–4 weeks before the chicks fledge or become independent. In this paper we investigate the costs and benefits of desertion for females. Desertion incurs a cost for females: following desertion chick survival in broods is lower (0.95 +- 0.02 day–1) than before the female deserts (0.98 +- 0.01 day–1). We investigated several possible causes for reduced brood survival by comparing characteristics of broods before and after desertion (controlling for differences in brood age). After desertion males increased the time they spent foraging and they tended to reduce time spent brooding chicks. Increased mortality of chicks may occur in deserted broods because following desertion (1) males spend less time alert in vigilance behaviour than before desertion, (2) they attend the chicks from greater distances, and (3) they show greater distraction display distances (in response to human intruders). Growth or development of chicks, measured by weight gain and tarsus length, was not different before and after desertion. Females gain two potential benefits from desertion: (1) they may remate and produce a second brood within the same breeding season or (2) they may enhance their probability of surviving to breed in a subsequent season. At least 27% of female kentish plovers that deserted remated and renested in the same season in this study. In contrast, we found no evidence that brood desertion increased the survival of females: there was no difference in local survival rate (return rate) for females deserting before or after 6 days brood age. These results clearly demonstrate that female kentish plovers that desert their offspring prior to fledging incur costs, but we suggest that there is a trade-off with the potential benefits gained by remating and making a second breeding attempt in the same season. 相似文献
17.
Noboru Okuda Tomohiro Takeyama Yasunobu Yanagisawa 《Behavioral ecology and sociobiology》1997,41(6):363-369
Entire-brood cannibalism by mouthbrooding males of the cardinal fish Apogon doederleini was investigated in temperate waters of southern Japan during two breeding seasons. The rate of cannibalism was 17–18% in
each season and did not differ among age-groups. However, the seasonal pattern of cannibalism differed markedly among age-groups:
young (1- and 2-year-old) males frequently cannibalized early broods, especially the first brood, of the season, whereas cannibalism
by middle-aged (3- and 4-year-old) and old (5- and 6-year-old) males mainly occurred late in the breeding season. We explain
this difference in terms of trade-offs between current and future reproduction. Young males, whose future reproductive success
is enhanced by the growth increment, may allocate more time and energy to growth by cannibalizing early broods. In contrast,
for older males who have had more breeding cycles and grow little, cannibalism could be a way to reverse the deterioration
in their somatic condition that occurs as the breeding season progresses. It is also likely that the current reproductive
loss entailed by the cannibalism is effectively compensated by quick re-mating with another female.
Received: 24 February 1997 / Accepted after revision: 20 July 1997 相似文献
18.
Genetic monogamy in the common loon (Gavia immer) 总被引:4,自引:0,他引:4
Walter H. Piper David C. Evers Michael W. Meyer Keren B. Tischler Joseph D. Kaplan Robert C. Fleischer 《Behavioral ecology and sociobiology》1997,41(1):25-31
We conducted behavioral observations and genetic analysis on breeding pairs of common loons in the upper Great Lakes region
from 1993 through 1995 to look for behavioral evidence of extrapair copulations (EPCs) and to determine parentage of young.
Pairs remained close to each other (usually within 20 m) during the pre-laying period, leaving little opportunity for EPCs
to occur. Males and females both maintained physical proximity by approaching each other when they became separated. Copulations
were obvious but infrequent, occurring about once every other day during the pre-laying period. Multilocus DNA fingerprinting
was consistent with behavioral findings: 58 young from 47 different families were all genetic offspring of parents that raised
them. Perfect genetic monogamy (genetic parentage of young by parents that rear them) in loons might arise as a consequence
of the need for vigorous territorial defense to prevent territorial takeover.
Received: 8 August 1996 / Accepted after revision: 22 March 1997 相似文献
19.
N. Saino C. R. Primmer H. Ellegren A. P. Møller 《Behavioral ecology and sociobiology》1999,45(3-4):211-218
The barn swallow (Hirundo rustica) is a socially monogamous passerine which usually breeds in colonies where extra-pair copulations are frequent. Males intensively
guard their mates during the female fertile period. Since males are more likely to be available for extra-pair copulations
when their mate is not fertile, synchrony in timing of breeding may affect paternity of individual males. In this study, we
analysed the change in mate-guarding rate by males in relation to the fertility condition of the female, and the relationships
between breeding synchrony and density with paternity in first broods of 52 male barn swallows. Paternity (proportion of nestlings
fathered in own brood) was assessed by typing of three highly polymorphic microsatellite loci. Mate guarding by males peaked
during the fertile period of their mates. Paternity increased as breeding synchrony in the colony increased. Paternity of
barn swallows is positively associated with the degree of exaggeration of male tail ornaments. The relationship between male
ornamentation and paternity was partly mediated by an effect of ornament size on breeding synchrony. We suggest that females
might delay breeding with low-quality males to enhance their opportunities for being fertilised by high-quality extra-pair
males.
Received: 16 January 1998 / Accepted after revision: 25 October 1998 相似文献
20.
We recorded behaviour of kestrels (Falco tinnunculus) in western Finland during the courtship (1988–1992), incubation (1989–1991), early nestling (age of young 1–2 weeks, 1989–1992) and late nestling stages (3–4 weeks, 1989–1991) to examine determinants of their parental effort (PE). In males, PE was estimated as the hunting effort (the proportion of budget time spent in flight-hunting) and in females as the food provisioning rate (number of prey items delivered to the nest per hour). The following predictions derived from the parental investment theory were examined. (1) Parents rearing large clutches and broods should invest more in breeding than do parents rearing small clutches and broods. The hunting effort of parents did not increase with clutch or brood size, but males tending large broods had a higher prey delivery rate than males tending small broods (Figs 1–2). (2) PE of parents should increase in the course of the breeding season. In males, this was true only between the incubation and early nestling phases (Fig. 3). (3) The early pairs should invest more in breeding than late ones. This tended to be true during the early (for males) and late nestling phases (for females) (Fig. 4). (4) There should be a negative correlation between PE of mates within pairs, but no evidence for such adjustment was found (Fig. 5). (5) Females mated with bright-coloured attractive males should show higher PE than females mated with dull-coloured males but our results were inconsistent with this prediction. We conclude that PE decisions of kestrels are mainly based on cost-benefit estimates of residual reproductive value, rather than on current investment indicators, like clutch or brood size. This might be beneficial in environments with highly variable survival prospects of offspring caused by pronounced among-year variation in abundance of the main food (microtine rodents). The results also show that hypotheses explaining variation in PE in the short term are not necessarily valid for long-term PE, e.g. tending clutches or broods, which also reflects the demands of female and young. 相似文献