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In several animal species, males offer material gifts to females during a courtship or precopulatory display. The provision of nutrients is a male investment that can increase female reproductive success; therefore males can use such gifts to influence female choice. Clear examples of courtship feeding before extrapair copulations are scarce, however. We investigated courtship feeding in the great grey shrike. Males offered food both to their mate and to extrapair females. Food offered to extrapair females had a significantly higher energy value than that offered to the social mates. The size of prey offered may enable females to judge a male’s quality. A larger gift resulted in a higher chance of copulation for males in both within- and extrapair events. We conclude that the energy value of nuptial gifts can explain why females of some species engage in extrapair copulations.
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Do males of the great grey shrike, Lanius excubitor,
trade food for extrapair copulations?
PIOTR TRYJANOWSKI* & MARTIN HROMADA†
*Department of Avian Biology and Ecology, Adam Mickiewicz University
yDepartment of Zoology, University of South Bohemia
(Received 28 August 2003; initial acceptance 9 October 2003;
final acceptance 17 June 2004; published online 11 November 2004; MS. number: 7835R)
In several animal species, males offer material gifts to females during a courtship or precopulatory display.
The provision of nutrients is a male investment that can increase female reproductive success; therefore
males can use such gifts to influence female choice. Clear examples of courtship feeding before extrapair
copulations are scarce, however. We investigated courtship feeding in the great grey shrike. Males offered
food both to their mate and to extrapair females. Food offered to extrapair females had a significantly
higher energy value than that offered to the social mates. The size of prey offered may enable females to
judge a male’s quality. A larger gift resulted in a higher chance of copulation for males in both within- and
extrapair events. We conclude that the energy value of nuptial gifts can explain why females of some
species engage in extrapair copulations.
Ó2004 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.
Female animals often copulate with males that are not
their social partners; however, their motivation is still
a matter of discussion (Birkhead & Møller 1992; Griffith &
Montgomerie 2003). Indirect genetic benefits are thought
to be the most important reason for this behaviour (Petrie
& Kempenaers 1998); however, direct, or nongenetic,
reasons are most readily understood (Kondoh 2001;
Møller & Jennions 2001). Direct fitness benefits have been
equated with the material benefits acquired by females,
and may derive from enhanced fertility, fecundity or
parental care obtained from mating with preferred males,
enhanced courtship feeding, higher quality of a breeding
territory, antipredator behaviour of a mate, or simply
the absence of directly transmitted diseases (Møller &
Jennions 2001).
A male’s reproductive success is limited by the number
of females with which he copulates, whereas a female’s
reproductive success is limited by her investment in
offspring (Trivers 1972). Thus, in general, males can be
seen as the competing sex and females as the choosing sex
(Atmar 1991; Kondoh 2001).
A female’s choice of mate can be influenced by a male’s
investment of resources or time in courtship. Nongenetic
benefits are an integral feature of the mating systems of
a variety of animals. Because the mating decision is
controlled primarily by females, males try to persuade
them by providing resources. Females prefer resources and
paternal ability that have a direct effect on their re-
productive success, and increase their fecundity (Møller
& Jennions 2001). There are many possible direct benefits
and they have been recorded in many animal taxa,
including insects, fish, reptiles, birds and mammals. Such
nongenetic benefits can comprise a territory with a crucial
resource (Cronin & Sherman 1977) or parental care (Smith
1979). Vigilant males, watching for predators, can also
allow females to spend more time foraging, collecting
food resources that will be needed to produce a clutch of
eggs (Artiss & Martin 1995).
The most common male investments in copulation are
those of a nutritional value, in the form of either male
secretions (Sakaluk 1984; Simmons 1990; Wedell 1993)or
prey items (Thornhill 1976; Stanford 1995), sometimes
even the male himself (Buskirk et al. 1984). None the less,
evidence of direct benefits in extrapair copulations are
surprisingly scarce.
One of the species offering food is the great grey shrike,
a raptor-like passerine bird, in which the male gives prey
(rodents, birds, lizards, or large insects) to females
immediately before copulation (Yosef 1992; Lorek 1995).
The species breeds mainly solitarily in pairs 500–1000 m
from one another (Scho
¨n 1994a). However, cases of mixed
reproductive strategy, polygamy and even extrapair
Correspondence: P. Tryjanowski, Department of Avian Biology and
Ecology, Adam Mickiewicz University, Fredry 10, PL-61 701 Poznan
´,
Poland (email: ptasiek@main.amu.edu.pl). M. Hromada is at the
Department of Zoology, University of South Bohemia, Branis
ˇovska
´
31, CZ-370 05 C
ˇeske
´Bude
˘jovice, Czech Republic.
529
0003–3472/04/$30.00/0 Ó2004 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.
AN IM AL BEH AV IO U R, 2005, 69, 529–533
doi:10.1016/j.anbehav.2004.06.009
copulations have been recorded (Yosef 1992; Lorek 1995;
Probst 2001).
Shrikes are well known for impaling prey on thorns and
sharp sprigs. Yosef & Pinshow (1989) have shown in an
experimental study that great grey shrike females select
a mate according to the size of prey impaled, with larders
thus serving as an extended phenotype of a male. If the
amount of food stored by the males can drive female mate
choice, food provided before within and extrapair cop-
ulations by males may also influence the female’s decision
to copulate. Larger prey are likely to require a greater male
investment in terms of hunting time and energy. There-
fore, we hypothesized that the size of the nuptial gift
should reflect a male’s quality. We then predicted that
females should choose those males that provide them
with larger precopulatory food items because they would
gain both direct and potentially indirect benefits. Conse-
quently, a male’s copulation success was predicted to be
related to the size of the nuptial gift.
The overall fitness of a particular male can be elevated
by extrapair copulations, with a single extrapair event
representing a greater chance of fertilizing eggs than one
of many within-pair copulations (Birkhead & Møller
1992). There is good evidence that female choice in
extrapair copulations is based on male traits (Houtman
1992; Hasselquist et al. 1996). Therefore, assuming our
first two hypotheses are correct, males should allocate
their courtship gifts strategically. If they actively seek
extrapair copulations, based on sexual selection theory,
they should offer larger prey to extrapair females.
METHODS
Study Species
The great grey shrike is a territorial, socially monoga-
mous bird. In the breeding season it defends large
territories covering ca. 20–50 ha (Scho
¨n 1994b). Pairs
produce a single brood each year, although replacement
clutches can occur after nest failures (Scho
¨n 1994a). Only
the female incubates, but young are fed and cared for by
both parents (Scho
¨n 1994a, b). Copulations are preceded
by precopulatory displays: the male faces the female,
shivers and flutters his wings and utters a call or a quiet
song, and often offers a food gift (Carlson 1989; Lorek
1995). The courtship-feeding intensity culminates several
days before the first egg is laid, when copulations are most
frequent (Lorek 1995).
Field Methods
We investigated the behaviour of the great grey shrike in
a high-density population (up to 24 breeding pairs/
100 km
2
) in western Poland, from the beginning of April
to mid-May in 1999–2002. Individuals were distinguished
by highly individual-specific wing patterns and eye-masks
(Scho
¨n 1994c; Probst 2001), and some (6–14 in different
years) were individually marked with colour rings under
licence from the Ringing Center Department of Ornithol-
ogy, Polish Academy of Sciences (for more details on study
sites and methods see Lorek 1995; Tryjanowski et al.
1999). Twenty-two males with both intra- and extrapair
copulation attempts recorded were included in the study.
We considered a copulation attempt unsuccessful when
courtship display (postures, wing shivering or courtship
singing) by the male near the female (up to 0.5 m) was not
followed by copulation itself. Because it was not possible
to observe cloacal contact, we considered a copulation to
have occurred when the mating event lasted for 3 s or
more (Lorek 1995).
Data Analysis and Statistics
To determine whether nuptial gifts can indicate male
quality, we correlated the value of food items (represented
as energy content, see Table 1 and details below) delivered
before copulation in within-pair attempts with the food
value of items delivered in extrapair attempts, for partic-
ular males. To avoid pseudoreplication, we examined and
used in the analyses only one observation of a male
bringing food for each category.
To test whether males use larger prey items to solicit
extrapair copulations, we compared the energy content
(details below) of food items in within-pair and extra-pair
gifts of all males, using the Wilcoxon matched-pairs
signed-ranks test.
We calculated the usable energy content of prey items
delivered as nuptial gifts from mean prey body size and
published values of gross energy (kJ/g) and metabolizable
energy coefficient (the proportion of overall energy con-
tent of the food item for a particular food item; Karasov
1990; Myrcha & Pinowski 1970; Table 1). Daily energy
demand of the great grey shrike was estimated to be 113 kJ
in the Negev Desert, Israel (Degen et al. 1992).
To establish the importance of food delivered before
copulation, we compared the mean energy value of the
nuptial gift with that of food delivered to a fertile female
outside of copulation events. Female birds are thought to
be fertile until the laying of the penultimate egg (Birkhead
& Møller 1992). Female great grey shrikes, which lay up to
eight eggs and start incubation from the third egg, are
thus potentially fertile until the fifth day of incubation
(Lorek 1995). Incubating females are fed almost exclusively
by their mates (our unpublished data, based on data
collected with digital cameras, from observations of 11
nests in the same study area), and thus males probably
provide a significant part of the female’s energy require-
ments during the fertile period.
To determine the male’s investment in nuptial gifts, we
investigated handling times (s) necessary for catching and
processing the prey (including chasing, killing, transport
and dismemberment of prey). We observed 47 cases of
great grey shrikes hunting in the study area. Only
observations where we saw the full spectrum of foraging
behaviour (from resting time to hunt procedures) were
included in the analysis.
Statistical tests were performed according to Zar (1999)
and all tests are two tailed. Data are presented as
mean GSD.
ANIMAL BEHAVIOUR, 69, 3
530
RESULTS
Males that offered courtship gifts of high energy value in
within-pair copulations also did so in extrapair events
(Spearman rank correlation: r
S
Z0.543, NZ17, PZ0.009).
The energy content of the nuptial gift in unsuccessful
copulation attempts (10.5 G15.1 kJ) was significantly
lower than in successful attempts (76.8 G135.5 kJ) in
within-pair events (Mann–Whitney Utest: UZ129.5,
N
1
Z8, N
2
Z22, PZ0.029) and in extrapair events (un-
successful: 36.1 G45.2 kJ; successful: 277.1 G185.2 kJ;
UZ212.0, N
1
Z11, N
2
Z22, PZ0.002).
Males offered different food items to extrapair females
than to their mates (Fig. 1). The mean energy content of
a gift offered to an extrapair female was nearly four times
higher (75.3 G56.3 kJ) than that for a male’s mate
(19.0 G39.0 kJ; NZ22 males that delivered food to both
an extrapair female and their mate; Wilcoxon matched-
pairs signed-ranks test; ZZ3.72, P!0.001). This repre-
sents 66.6 versus 16.8% of the female’s daily energy
requirement, respectively. The mean energy delivered
by a male to an incubating fertile female was
19.0 G30.2 kJ/h (16.8% of the female’s daily energy
requirement, NZ11 nests) and comprised an average of
one prey item/h.
The prey most frequently offered to extrapair females
(vertebrates) was more costly for males in terms of time
spent hunting. The handling time of hunting shrikes was
significantly longer for vertebrate (33.0 G32.6 s) than for
invertebrate prey (5.5 G2.6 s; Wilcoxon matched-pairs
signed-ranks test: ZZ3.41, NZ16, P!0.001).
DISCUSSION
We have shown that the value of the courtship gift could
indicate a male’s quality. Males that offered larger prey to
their mate also did so when soliciting extrapair copula-
tions. Courtship gifts signalling the quality or rank of the
male have been recorded in a variety of animals, such as
hanging flies, Hylobittacus apicalis, and chimpanzees, Pan
troglodytes (Alcock 1998). Great grey shrike males that were
able to offer larger (and more energy-rich) food items
before copulation were more often selected as sexual
partners. Female shrikes may choose the male before
copulation, just after the gift is delivered.
Copulation success of the males was significantly higher
if they offered larger and more energy-rich prey. This was
true for both intrapair and extrapair copulations; no
extrapair copulations were successful without a gift pro-
vided.
Male great grey shrikes contributed considerably to the
nutrition of their mates during the fertile part of the
incubation period by providing a substantial proportion of
the female’s daily food requirement. This means that
males allocated their courtship gifts strategically to copu-
lation attempts that could improve their overall fitness
more dramatically. This finding corresponds with the
predictions of sexual selection theory (Birkhead & Møller
1992).
Until recently, females were thought to gain only
indirect, genetic, benefits from seeking extrapair copula-
tions (Petrie & Kempenaers 1998). Other examples of
direct benefits to females from extrapair matings are scarce
in the literature. Female red-winged blackbirds, Agelaius
phoeniceus, primarily a polygamous bird, may gain in
terms of increased foraging opportunities on the territory
of her extrapair mate and from additional defence against
nest predators from this male if he is in a neighbouring
territory (Gray 1997). In the purple-throated humming-
bird, Eulampis jugularis, males provide cooperative females
with access to food sources in their territories, exchanging
food for copulation even during the nonbreeding season
(Wolf 1975). The only known example of similar behav-
iour in a socially monogamous species is the Ade
´lie
penguin, Pygoscelis adeliae, in which males exchange nest
material for copulations (Hunter & Davis 1998).
For males, seeking extrapair copulations is thought to be
a trade-off between investing in mate guarding and
parental care (Westneat et al. 1990). Nevertheless, in male
great grey shrikes the fertilization benefits of precopulatory
Table 1. Energy content of food items offered by great grey shrike males to females before copulation
Prey
DM/prey
individual (g) GE (kJ/g)
OE/prey
individual (kJ) MEC
ME/prey
individual (kJ) DE (%) PR
Passer montanus 3.20 21.8 69.76 0.75 52.32 46.3 2.4
Microtus arvalis 4.20 23.5 98.77 0.75 74.08 65.6 1.5
Lacerta sp.0.83 22.1 18.26 0.75 13.69 12.1 8.2
Gryllus campestris 0.25 23.2 5.87 0.77 4.52 4.0 25.0
DM: Dry mass (our data and Myrcha & Pinowski 1970 for P. montanus): GE: gross energy, kJ/g dry mass (Karasov 1990); OE: overall energy
content (DM !GE); MEC: metabolizable energy coefficient (Karasov 1990; we used a coefficient of 0.75 for all vertebrates and the value for
G. domesticus for G. campestris); ME: metabolizable energy (OE !MEC); DE: % of bird’s daily energy requirement provided by one prey
individual (Degen et al. 1992); PR: number of prey required for bird’s daily energy requirement.
0
2
4
6
8
10
12
14
Number of prey items
Birds Voles Lizards Insects Without
g
ift
Fig. 1. Number of nuptial gifts offered by males to females in within-
pair (,) and extrapair (-) copulations. Prey are shown by
taxonomic group. Gtest: G
12
Z22.87, PZ0.029.
TRYJANOWSHI & HROMADA: MALE SHRIKES BUY SEX 531
gift giving must be weighed against the costs of acquiring
such gifts. The capture of the larger vertebrate prey
required higher energy expenditure because the shrikes
had to chase them for longer than other prey. Furthermore,
if a male invests more time in hunting to obtain a suitable
nuptial gift for an extrapair copulation, he risks being
cuckolded himself. Whatever the risks, the tendency of
male shrikes to invest more in extrapair events suggests
some potential benefits of this activity. We suggest that the
behaviour observed in male great grey shrikes reflects the
greater fitness benefits of a single successful extrapair event
than multiple within-pair copulations. The investment of
males in reproduction within a pair is high: they defend
a territory, participate in nest building, and feed and guard
their mates and offspring. By contrast, the only investment
in an extrapair copulation is food.
Direct benefits for great grey shrike females were
obvious in our study. Possible genetic advantages should
be investigated further. If male ability to obtain valuable
prey is somehow heritable, females may gain both direct
and indirect benefits by choosing the male that provides
them with the most valuable prey. However, mating with
extrapair males could be costly. Females of the lesser grey
shrike, Lanius minor, that engage in copulation with other
males are sometimes punished by males (Valera et al.
2003). The female could also be risking divorce and
a reduction in their partner’s investment (Valera et al.
2003). This may be why females have higher standards in
extrapair than within-pair copulations. Hence, the ob-
served pattern may arise from a balance between the costs
and benefits of extrapair copulations to a female.
We investigated the possible motivation of male shrikes
for extrapair copulations. However, multiple mating by
female birds is also interesting. There is evidence that
mating with more than one partner is widespread in
females of many animal taxa, from insects to mammals
(Kondoh 2001). Material-benefit polyandry, or prostitu-
tion polyandry (Alcock 1988), is the most readily un-
derstood of several hypotheses for multiple mating by
females. It states that both the females engaging in
multiple mating and the males providing the direct
benefit play essential roles in the evolution of polyandry.
Therefore, the question arises: why has evidence for direct
benefits in extrapair copulations been so scarce?
Future studies should investigate whether males that
invest more really can increase their chances of reproduc-
tive success through extrapair offspring. If not (which is
possible, see Valera et al. 2003), what exactly do both
extrapair partners obtain from sexual contact with each
other?
Acknowledgments
We thank G. Lorek, M. Antczak, J. Grzybek, P. Czechowski,
P. Kaczorowski and P. T. Dolata for their field assistance,
as well as P. Chylarecki, K. Halupka, I. Hromadova
´,
P. F. Donald, F. Proffitt, P. Bellamy, T. H. Sparks, F. Sergio,
F. Valera, T. J. Valone and two anonymous referees for
helpful comments. R. Fuchs loaned us a video recorder
for the research. This research was funded by Adam
Mickiewicz University, Poznan
´, Poland, GEF/SGP Poland
grants and SGA grant of University of South Bohemia,
C
ˇeske
´Bude
ˇjovice, Czech Republic. The financial support
for data analyses was provided by a grant from the State
Committee for Scientific Research (6 PO 4F 04621).
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TRYJANOWSHI & HROMADA: MALE SHRIKES BUY SEX 533
... Nuptial gifts, in general, convey the information about male attractiveness or quality, and females often prefer gift-giving males 10,27 There is also a clear link between nuptial gifts and sexual selection that occurs after mating 2 . Like D. melanogaster, the female red our beetle Tribolium castaneum store more sperm when mating with well-fed males than when mating with starved males 28 . ...
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Nuptial gift-giving or courtship feeding is prevalent across. In an extreme case, females eat male body parts; in another case, females derive nutrients from males’ seminal fluids1. The nursery web spider, Pisaura mirabilis, females store more sperm from nuptial gift-giving males than those offering no gift with the identical copulation duration2. However, it is not known how females evaluate nuptial gifts and adjust sperm storage. Here, we show that Drosophila melanogaster females hold the ejaculate of starved males for shorter period and store less number of their sperm. A knock-down of the sugar transporter Tret1-1 in neurons that express the neuropeptide diuretic hormone 44 (Dh44-PI) critical for the ejaculate holding3 and detection of the nutritional value of sugar4 impairs the female’s ability to adjust the ejaculate holding period according to the male energy status. A galactoside selectively present in the male ejaculate activates Dh44-PI neurons in the brain to secrete Dh44, and starvation reduces its production by approximately 50%. RNAi-knockdown of glycosyltransferases, including UGT305A1, allows males to produce significantly lower amounts of the galactoside without starvation. Females mated with UGT305A1 knockdown males hold the ejaculate shorter, store less sperm and lay fewer eggs. The seminal galactoside enters the female hemocoel during mating, stimulates the activity of Dh44-PI neurons in the brain, augments the secretion of Dh44, and increase the ejaculate holding period, thereby enabling the uptake of injected nutrients and sperm. These evidence suggest that the galactoside signals reflecting the quality of male partners increase sperm storage and may be a source of nutrients used for egg production. Together, this study provides a molecular and cellular framework for understanding how females evaluate courtship feeding and optimize sexual selection after mating.
... For example, females may obtain resources from extrapair males. Male great gray shrikes (Lanius excubitor) o er prey as nuptial gifts to both within-pair and extrapair females, but the prey gifted to extrapair females is signi cantly larger than that gifted to social mates (Tryjanowski & Hromada, 2005). In this population, females can obtain direct bene ts from in delity both in the form of extra energy from nuptial gifts and an increased number of o spring. ...
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Infidelity occurs in many socially monogamous animals. While infidelity may affect both sexes via sexually transmitted diseases, in general infidelity is beneficial to mated males but more often costly to mated females. Unfaithful females are therefore expected to receive either direct benefits (i.e., benefits increasing female survival, offspring survival, or number of offspring), indirect benefits (i.e., genetic benefits increasing the number of grandoffspring), or both, in order to balance the costs of infidelity. However, recent meta-analyses have provided only limited support for these adaptive explanations of female infidelity. Emerging hypotheses therefore posit that infidelity might be nonadaptive to females and is presumably maintained in females as a byproduct of other traits favored by selection. This chapter discusses our current understanding of the potential consequences of infidelity in socially monogamous nonhuman animals, including costs and benefits for both sexes, and suggests directions for future studies.
... Such negative effects (or constraints) may be avoided by mating outside the social pair bond (i.e. extra-pair mating), although extra-pair paternity (EPP) generally only provides indirect genetic benefits to the offspring and no direct benefits to the female (but see [15][16][17]). Species with high between-season divorce rates were found to have high EPP [18], supporting the hypothesis that the two are complementary secondary mating strategies and that the rates of both behaviours are higher in species with larger variation in mate quality. ...
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Individuals of socially monogamous species can correct for suboptimal partnerships via two secondary mating strategies: divorce and extra-pair mating, with the former potentially providing both genetic and social benefits. Divorcing between breeding seasons has been shown to be generally adaptive behaviour across monogamous birds. Interestingly, some pairs also divorce during the breeding season, when constraints on finding a new partner are stronger. Despite being important for a comprehensive understanding of the evolution of social monogamy, whether within-season divorce is adaptive and how it relates to extra-pair mating remains unknown. Here, we meta-analysed 90 effect sizes on within-season divorce and breeding success, extracted from 31 studies on 24 species. We found no evidence that within-season divorce is adaptive for breeding success. However, the large heterogeneity of effect sizes and strong phylogenetic signal suggest social and environmental factors—which have rarely been considered in empirical studies—may play an important role in explaining variation among populations and species. Furthermore, we found no evidence that within-season divorce and extra-pair mating are complementary strategies. We discuss our findings within the current evidence of the adaptiveness of secondary mating strategies and their interplay that ultimately shapes the evolution of social monogamy.
... Female birds cannot take advantage of increased fecundity (the number of eggs in a clutch) from EPC, however, in socially monogamous relationships, females may mate multiply because of indirect genetic (e.g., 'good' and 'compatible genes' hypothesis) ( [11,19,[27][28][29][30][31], but see [26,32]) and direct benefits. Direct benefits include, for example, a better chance of fertilization of eggs [33], nuptial gifts from several mates [34,35], but see [36], or getting extra help from extra-pair mates in caring for offspring at the nest [18,37,38]. By mating with extra-pair males, females may construct a social network, which also could provide benefits to them (vigilance, alarm calls, calling networks, predator mobbing, and so on) [24,39]. ...
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Extra-pair copulation (EPC) occurred in most socially monogamous bird species. The mechanisms leading to the frequent occurrence of extra-pair offspring (EPO, EPY) in socially monogamous couples, as well as the ‘function’ of EPC, are the subjects of strong debates and raise many unanswered questions. We studied the relationship between extra-pair paternity (EPP) and the different characteristics of males and females in the European pied flycatcher in Western Siberia (Russia). The analysis was based on the genotyping of 232 males, 250 females, 1485 nestlings (250 nests). The European pied flycatchers were predominantly socially and genetically monogamous, but about 20% of birds could be involved in EPP. Loss of paternity tended to be more frequent in one-year-old males. EPCs could be multiple: one individual may have up to three extra-pair partners. The EPP rate was independent of the breeding time. The extra-pair mates of an individual were mainly its near neighbours. The EPC status of an individual was unrelated to most of its morpho-physiological traits. The occurrence of EPP was almost twice as high in females nesting in good quality territories. The fitness of within-pair offspring, EPO, paternal half-sibs of EPO and maternal half-sibs of EPO did not differ statistically significantly. Assuming very low heritability of extra-pair mating, we argued that EPCs could be incidental side effects (by-product) of selection. We believe that the evolution and maintenance of extra-pair mating are the episelective processes in the case of the European pied flycatcher.
... The benefit of EPP to females is less clear, however; while not increasing the number of offspring that they produce, it may include (1) indirect fitness benefits through better genes, and (2) direct material benefits by trading copulation for food with extra-pair males (e.g. Tryjanowski and Hromada 2005). Indirect genetic benefits could be good paternal genes and genetic compatibility of maternal and paternal genomes (Kempenaers 2007;Puurtinen 2009;Arct et al. 2015). ...
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Patterns of extra pair paternity (EPP) and intraspecific brood parasitism (IBP) were studied in a Whiskered Tern Chlidonias hybrida population characterized by female brood desertion, a high level of extra pair courtship feedings (10%) and a low level of extra pair copulation (EPC; 0.6%). In this study, we used a set of microsatellite loci to analyse parentage in 56 Whiskered Tern families from southern Poland. Depending on the method, we detected that 1.4%–3.6% of chicks were sired by an extra-pair male, and extra-pair chicks were present in 3.6%–8.9% of broods. IBP was observed in 8.9%–14.3% of broods, corresponding to 3.6%–6.4% of the chicks. The low rate of EPP is in agreement with the hypothesis that in species with high male parental investment, females should avoid EPC. The low level of IBP indicates that intraspecific egg dumping is not a common female strategy in Whiskered Tern, similar to many other colonial waterbird species.
... Display, wherein males attempt to maximize fitness by attracting reproductive females to mate, is known to drive SSS [6]. The subject of display has been found to occur in a wide range of empirical studies such as quantity and quality of prey [7,8], color and ornamentation [9], vocalizations [10], ritual dance [11], chemical [12], and several other qualities that Zahavi collated under the "Handicap Principle" [13,14]. ...
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Display, wherein males attempt to maximize fitness by attracting sexually mature females to mate, is known to drive speciation by Sexual Selection. We researched the Red Sea Ghost Crab (Ocypode saratan; RSGC), in which males build display pyramids to attract females. The study was conducted at the beach in Eilat, Israel. At each session, we measured the height (in cm) of all pyramids and the dimensions (height, breadth; in cm) of the burrow entrance. We assumed that the size of the entrance represented the relative size of the carapace width of the occupant. The mean (± SE) entrance volume was 230.8 ± 11.7 cm and the height of the pyramid was 11.8 ± 0.49 cm (N = 54). The results of our study did not support our hypothesis because we had expected to find a linear correlation between body size and pyramid height, i.e., the larger the male, the larger the pyramid. However, our results show that the largest males in the population either built small pyramids or not at all; and the cut-off of the larger crab’s body size appears to be around 350 cm3. We discovered a step-wise function in the data in that crabs with the smallest body size of ca. 250cm3 constructed the highest pyramids, with a declining tendency between 250-350 cm3, and extremely low pyramids beyond 350 cm3. However, our findings need to be further studied with a stress on the ambiance and to elucidate whether the habitats differ in temperature, humidity, prey-base, etc. before concluding as to why the larger males desist from building pyramids. This study underwrites the importance of studying the mating systems of the macro-fauna of the beaches that are fast disappearing owing to anthropogenic development.
... These critiques have pointed to errors inherent in measurement (Bettinger 1991;156 Bettinger 1987; Grayson and Cannon 1999), the possibility that other variables are equally, or more 157 important than, Kcals (e.g. Belovsky, 1987 good reason to believe that both biological (e.g., Simpson et al. 1999;Tryjanowski & Hromada 2005) and 160 material cues (e.g., Mills & Ferguson 2008;Neiman 1997) served to display social status, esoteric 161 ...
... The self-domestication hypothesis also emphasizes the importance of reduced reactive aggression and violent conflict between male individuals, not females, as an important factor for the evolution of human-like prosociality (Wrangham, 2019). Beyond that, prosocial actions might represent an attempt of males to trade food for extra-pair copulations (Tryjanowski and Hromada, 2005) or to maintain relationships with affiliative partners other than the mated partner (Miyazawa et al., 2020;von Bayern et al., 2007;Boucherie et al., 2016). In general, the results from the single sex models -especially the femaleonly model -have to be considered preliminary due to the low sample size. ...
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The investigation of prosocial behavior is of particular interest from an evolutionary perspective. Comparisons of prosociality across non-human animal species have, however, so far largely focused on primates, and their interpretation is hampered by the diversity of paradigms and procedures used. Here, we present the first systematic comparison of prosocial behavior across multiple species in a taxonomic group outside the primate order, namely the bird family Corvidae. We measured prosociality in eight corvid species, which vary in the expression of cooperative breeding and colonial nesting. We show that cooperative breeding is positively associated with prosocial behavior across species. Also, colonial nesting is associated with a stronger propensity for prosocial behavior, but only in males. The combined results of our study strongly suggest that both cooperative breeding and colonial nesting, which may both rely on heightened social tolerance at the nest, are likely evolutionary pathways to prosocial behavior in corvids.
... This is because females' reproductive output is limited by their reproductive biology rather than by their number of mates. There are the potential direct fitness benefits for females involving in EPCs (for example, fertilisation assurance of eggs, nuptial gifts from several mates, increased paternal care at nest, cooperative neighbourhood) (Stacey, 1982;Davies, 1992;Sheldon, 1994;Davies et al., 1996;Arnqvist & Nilsson, 2000;Tryjanowski & Hromada, 2005;Eliassen & Jørgensen, 2014) as well as the potential direct costs (sexually transmitted disease, reduced paternal care by the within-pair social mate) (Beemer, Kuttin & Katz, 1973;Davies, 1992;Sheldon, 1993;Davies et al., 1996;Lombardo & Thorpe, 2000;Houston, Szekely & McNamara, 2005). Strong natural selection would seem to effectively eliminate the variation in infertility in individuals (but see, e.g. ...
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Males and females take part in extra-pair copulations in most socially monogamous bird species. The mechanisms leading to the frequent occurrence of extra-pair offspring in socially monogamous couples are strongly debated and unresolved, and they are often difficult to distinguish from one another. Most hypotheses explaining the evolution of extra-pair reproduction suggest selective and adaptive scenarios for their origination and persistence. Is extra-pair paternity a heritable trait? We evaluated the heritability of extra-pair paternity in the pied flycatcher (Ficedula hypoleuca) nesting in Western Siberia. Estimated heritability was low: depending on the model used, the point estimate of the heritability (mode) varied from 0.005 to 0.11, and the bounds of the 95% confidence interval are [0-0.16] in the widest range. Thus, it seems that extra-pair mating behaviour in the pied flycatchers is a plastic phenotypic mating tactic with a small or no genetic component. Our data can help to understand the evolution of extra-pair mating behaviour in socially monogamous species.
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Extra‐pair paternity (EPP) benefits to improve the reproductive success via extra‐pair fertilizations without the costs of parental care in males and through improved offspring quality with additional food and parental care in females among species of birds. Variations in the EPP appear to link to behavioral and ecological factors and sexual selection. According to the “relationship intelligence hypothesis” (RIH), the cognitive abilities of the birds play an important role in maintaining long‐term relationships. Here, we undertook the first comparative test of the relationships between extra‐pair paternity and brain size, testis size and life histories among 315 species of birds using phylogenetically controlled comparative analyses and path analysis. After controlling for the effects of shared ancestry and body mass, the frequency of the EPP was negatively correlated with relative brain size, but positively with testis size across species of birds. However, the frequency of the EPP was not linked to life‐history traits (e.g., incubation period, fledging period, clutch size, egg mass and longevity). Our findings suggest that large‐brained birds associated with enhanced cognitive abilities are more inclined to maintain long‐term stable relationships with their mates and to mutualism with them than to increase the frequency of the EPP. This article is protected by copyright. All rights reserved
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Habitat composition of breeding territories, habitat use during foraging, and nest-site selection of the Great Grey Shrike Lanius excubitor were examined in western Poland during years 1998-1999. Meadows and spring crops occurred within territories more frequently than expected by their availability. Habitat utilisation during foraging was significantly non-random and shrikes appeared to prefer low vegetation. All of 27 nests were located along tree lines and edges of small woodlots (maximum 7 m), and neither deciduous nor coniferous trees were preferred (78% and 22%, respectively). Preferred habitats of Great Grey Shrikes are relatively uncommon in modern agricultural landscape. Lack of suitable habitats in intensively used farmland may be the most important reasons for strike population decline over Europe. Wielkopolska region offers good breeding habitats and this species has more dense and stable population over here, than in other parts of Europe.
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material is in the form of small stones used to create a platform on which the female lays her two eggs. Stones are in great demand in the colony and are collected by both males and females from the ground in the area surrounding the breeding group (Sladen 1958). In addition, individuals regularly steal stones from the nest sites of other individuals (Sladen 1958). Any individual approaching a male at his nest site and taking a stone is met with an aggressive response from the site-holder (Spurr 1975a). Site-holders will peck, "flipper-bash," and chase stone-stealers. The benefit of collecting and defending a large pile of stones is realized under particular weather conditions, usually in springtime, when meltwater can inundate the breeding colony. Flooding by meltwater can result in nest desertion and egg loss (Taylor 1962). Moreno et al. (1995) found that in the closely related Chinstrap Penguin (Pygoscelis antarctica), which displays similar stone-collecting behavior to the Ad61ie Penguin, large nests were less likely than small nests to fail as a result of flooding by meltwater. Moreno et al. (1995) concluded that stone collecting and nest maintenance improved nest quality and increased reproductive success. Ad61ie Penguins are monogamous and breed in large colonies in Antarctica. They engage in courtship and copulation behavior during the prelaying period, which spans from mid-October to the end of