Do female great tits (Parus major) assess males by eavesdropping? A field study using interactive song playback

Male singing behaviour correlates with extra-pair success in several passerine birds. Singing interactions during territorial contests provide relative information on the males involved. Such information may be important in female extra-pair behaviour and eavesdropping on singing interactions among males may allow females to make such relative assessments. We used interactive playback to instigate singing contests with male great tits during the peak fertile period of their mate in an attempt to alter females'' assessment of mates'' quality relative to neighbours (potential extra-pair partners). We escalated a contest to one male (by overlapping his songs) and then subsequently de-escalated a contest (by alternating) to a neighbour. Intrusions onto neighbouring territories by females mated to either treatment male were then monitored. Females mated to escalation treatment males were more likely to intrude following playbacks than females mated to de-escalation treatment males. Although the absolute song output of males did not differ between treatments, males produced more song relative to playback in de-escalation treatments and relative song output was positively correlated with female intrusions. Therefore, female great tits eavesdrop on singing interactions and change their visitation rates to neighbouring territories according to their mate''s singing performance relative to neighbours.     

Are colorful males of great tits Parus major better parents? Parental investment is a matter of quality

Given the known influence of parental investment on breeding success of great tits Parus major, females should be expected to use male parental quality as an essential criterion in mate choice. Since parental quality cannot usually be observed directly at the time of pairing, it has been suggested that females rely on male ornaments as indicative of their ability to provide parental care. This hypothesis, called the good parent hypothesis, has been tested repeatedly assessing only parental effort as the number of feedings made by parents. However, in evaluating parental investment, the focus should also be on the quality of prey captured rather than only on its quantity. We analyzed feeding rates and the provisioning of different prey in relation to both male yellow carotenoid-based breast coloration and the size of the black melanin-based stripe in a Mediterranean great tit population. We predicted that more carotenoid ornamented individuals would feed nestlings with a diet consisting of a higher proportion of caterpillars. However, and contrary to predictions, we found that males with higher values of hue in the yellow breast feathers, fed their offspring with a lower proportion of caterpillars and a higher proportion of spiders. In addition, nestlings that received a higher proportion of spiders showed an improved body condition after controlling for tarsus length and other variables. Male feeding rates correlated positively with brood size and tended to correlate negatively with date, although we did not find any effect of male coloration. Our data therefore support the good parent hypothesis, insofar as parental investment is also a matter of quality, and that, at least in the Mediterranean area, caterpillars are not the only key food source.     

Do Great Tit Parus major parents gear their brood defence to the quality of their young?

Parental investment theory suggests that animals should increase their reproductive success by investing more heavily in higher-quality offspring than in lower-quality offspring. Great Tit Parus major nestlings of higher body weight have been shown to enjoy a higher survival rate after fledging. We examine for the first time whether Great Tit parents invest more heavily in heavier nestlings as measured by defence (six variables) against a Pygmy Owl Glaucidium perlatum, similar to G. passerinum, which is a predator of both adult and nestling birds including hole-nesters like the Great Tit. Thirty-two parent Great Tit pairs in a wood- and parkland study area in Essen-Stadtwald did not vary their antipredator behaviour in relation to nestling weight; between-brood variation of weight was similar to that found in different populations and in different years. However, parental defence behaviour varied, as expected, with parent's sex and nestling number, though overall responsivity of parents to many other independent variables appeared lower than found previously.     

Do extra‐pair paternities provide genetic benefits for female blue tits Parus caeruleus?

A large body of theories on extra-pair paternity (EPP) in birds has proposed four main "genetic" hypotheses to explain this behaviour: the "good genes" hypothesis, the genetic diversity hypothesis, the genetic compatibility hypothesis and the fertility insurance hypothesis. Empirical tests have been scarce, mainly because high sample sizes are difficult to collect. We have tested these hypotheses in three Mediterranean populations of blue tits Parus caeruleus in which 50–68% of the broods contained extra-pair young. Results showed that the distribution of extra-pair young among broods was not random, and that survival to fledging of extra-pair young was higher than that of their within-pair sibs. These results support the idea of genetic effects benefiting extra-pair young. However, comparison of cuckolded and cuckolding males showed no significant difference in their body size, age, survival or relatedness with their paired females, and offspring morphometrics did not differ between extra-pair and within-pair young. We conclude that none of the genetic hypotheses can explain fully the high level of extra-pair paternity, at least in our populations of Mediterranean blue tits. We suggest that direct ecological benefits of EPP for females should be tested more often in correlative as well as experimental approaches.     

Do sibling tits (<Emphasis Type="Italic">Parus major,P. caeruleus</Emphasis>) disperse over similar distances and in similar directions?

We studied dispersal movements by sibling pairs of great tits, Parus major, and blue tits, P. caeruleus, in a patchy environment, in order to test whether siblings are more similar in dispersal than expected by chance. Because of possible common environmental effects due to the heterogeneity and finiteness of the study area, we compared the similarity among siblings with the similarity between each sibling and an unrelated bird that fledged in the same patch and year, as close to the siblings nest as possible. Siblings of both species were not more similar in dispersal distance than they were to control birds. However, great tit siblings dispersed in similar directions compared to control birds, and this result was not affected by the degree of matching between sibling and control birds. As a consequence, siblings ended up breeding at closer distances from one another than control birds. Heritability values calculated from parent-offspring regressions were close to zero, suggesting that there is no additive genetic variance for dispersal distance or dispersal direction. We propose that similarity in dispersal direction originates from association of siblings during dispersal or during activities that influence the choice of direction, such as postfledging family movements. Our results show that non-independence in the choice of dispersal direction by siblings may influence small-scale kin structure in this population with high local recruitment.     

Do great tits assess rivals by combining direct experience with information gathered by eavesdropping?

Animals frequently use signals that travel further than the spacing between individuals. For every intended recipient of a given signal there are likely to be many other individuals that receive information. Eavesdropping on signalling interactions between other individuals provides a relatively cost-free method of assessing future opponents or mates. Male great tits (Parus major) extract relative information from such interactions between individuals unknown to them. Here, we show that male great tits can take information gathering a stage further and obtain more information about a previously unencountered intruder, by the hitherto unknown capability of combining information gathered by eavesdropping with that derived from their own direct interaction with an individual. Prior experience with an intruder (A) was achieved by subjecting a focal male to different levels of intrusion simulated using interactive playback. This intruder (A) then took part in a simulated interaction with an unknown male (B) outside the territorial boundary of the focal males. In response to subsequent intrusion by the second male (B), focal males showed low song output in response to males that had lost to a male that the subject was able to beat. Males of known high quality, or those about which information was ambiguous, elicited a high level of song output by focal males. We discuss the implications of this finding for the evolution of communication and social behaviour.     

Importance of conspicuous colours in warning signals: the great tit’s (Parus major) point of view

Few studies have dealt with the importance of colours per se in warning signalling, with the use of a broader array of different colours. We tested the reactions of great tits (Parus major) to colour modifications (red, orange, yellow, white, blue, violet, and green) of the warning signal of the red firebug (Pyrrhocoris apterus), preserving its typical black pattern. We used the edible Guyana spotted roach (Blaptica dubia) as the prey, each of which carried a paper sticker shield of a particular colour on its back. With such prey, the effects of the other traits of the red firebug (e.g. shape of the legs and antennae or chemical signals) on the birds’ reactions were removed. All of the conspicuous forms of the prey, possessing a black pattern, were protected against great tits better than the non-patterned brown control form. The level of protection decreased from those forms with colours similar to the model and commonly occurring in warning signals in nature (red, orange, yellow), through other conspicuous colours rarely occurring in warning signals in nature (white, violet, blue), to the colour which usually occurs as cryptic in nature (green). In the green form, repeated encounters were necessary to reach avoidance. Avoidance learning came to pass despite the fact that the presented prey was neither inedible nor distasteful.     

Is hissing behaviour of incubating great tits related to reproductive investment in the wild?

Anti-predator behaviour of breeding animals is a complex trait that depends on current reproductive investment as well as individual differences in risk-taking propensities. In response to nest predation, many bird species produce specific sounds, such as the hissing calls in incubating great tits (Parus major), that may provoke an acoustic startle response in the predator. However, it is still unclear whether the propensity of incubating females to produce hissing calls towards nest predators depends on the reproductive investment. With our 3-year study, we show that response type (females that do not hiss versus females giving hissing calls) to a potential nest predator, the woodpecker, is a repeatable trait. We found no differences in the studied reproductive traits between hissing and non-hissing birds. Interestingly, among hissing birds, fast-responding females started egg-laying earlier than slow-responding ones. Among non-hissing birds, heavier birds initiated clutches earlier. We also revealed that hissing birds breed in areas with decreased nest-box occupancy, suggesting either that they potentially select different areas to breed or that territory size is larger as a result of hissing birds being more aggressive. These findings demonstrate that response type is not related to the early reproductive value of the brood across distinct behavioural groups. However, our results do suggest that non-hissing and hissing females differ in terms of individual quality or dominance or personality related aspects.     

How does an increase in minimum daily temperatures during incubation influence reproduction in the great tit Parus major?

Temperature variation affects all life stages of organisms, especially early development, and considering global warming, it is urgent to understand precisely its consequences. In egg‐laying species, incubation behaviour can buffer embryo developmental temperature variation and influence offspring development. We experimentally investigated the effect of an increase in minimum daily nest temperature during incubation in the great tit Parus major, by placing a hand warming pad under the nest in the evenings. As compared to controls, the experimental treatment increased nest temperature at night by an average of 4°C, and this increase carried over to the following day. We measured the consequences of this mainly nocturnal temperature increase during incubation on 1) parental behaviour (incubation and nestling feeding), 2) parental health (quantified by body condition, immune status, physiological and oxidative stress) and 3) reproductive success (nestling body condition, growth, i.e. mass gain, hatching and fledging success, and nestling immune status, physiological and oxidative stress). This study yielded three major results. First, we found that heating the nest did not change the duration of incubation as compared to controls. Second, increasing nest temperature during incubation decreased nestling feeding behaviour but did not affect parental health in terms of body condition, immune status, physiological and oxidative stress. Third, nestling mass at hatching was greater but nestling mass gain was slower in heated nests than in control nests, resulting in similar fledging mass. The present study demonstrates that increased environmental temperatures during incubation influenced nestling development in the great tit and especially hatchling mass, which might produce long‐term life history consequences.     

Are avian blood parasites pathogenic in the wild? A medication experiment in blue tits (Parus caeruleus).

The Hamilton and Zuk hypothesis on haemoparasite-mediated sexual selection and certain studies of reproductive costs are based on the assumption that avian blood parasite infections are detrimental to their hosts. However, there is no experimental evidence demonstrating harmful effects of blood parasites on fitness in wild populations, it even having been suggested that they may be non-pathogenic. Only an experimental manipulation of natural blood parasite loads may reveal their harmful effects. In this field experiment we reduced through medication the intensity of infection by Haemoproteus majoris and the prevalence of infection by Leucocytoazoon majoris in blue tits (Parus caeruleus), and demonstrated detrimental effects of natural levels of infection by these common parasite species on host reproductive success and condition. The fact that some of the costs of infection were paid by offspring indicates that blood parasites reduce parental working capacity while feeding nestlings. Medicated females may be able to devote more resources to parental care through being released from the drain imposed upon them by parasites and/or through a reduced allocation to an immune response. Therefore, this work adds support to previous findings relating hosts' life-history traits and haematozoan infections.     

Numerical and behavioural responses of migrant passerines to experimental manipulation of resident tits (Parus spp.): heterospecific attraction in northern breeding bird communites?

Summary We studied experimentally interspecific competition among foliage-gleaning passerine birds by manipulating the density of resident tits. In 1988 tit density was experimentally increased on three small islands in a central Finnish lake, and decreased on three other islands by tit removal. In order to avoid the effects of between-island differences in habitat quality, the role of the islands was reversed when the experiment was repeated in the following year. Censuses and observations on foraging and feeding behaviour were conducted to assess the numerical and behavioural responses of migrant conguilders (mainly chaffinches and willow warblers) with respect to the manipulated abundance of the tits. We also measured whether variation in food consumption of tits affected the frequency with which the migrants found food by calculating average intervals between successful prey captures, time lags to prey-capture and giving-up times. Our results indicate that interspecific competition is of minor importance in structuring breeding bird assemblages and species feeding ecologies on the study islands. No consistent difference in foraging or feeding niches of chaffinches and willow warblers was found between low and high tit density conditions. Niche overlap analysis showed no avoidance by chaffinches and willow warblers of the microhabitats which tits used. Tit abundance had no significant effect on feeding success or behaviour. Experimentally increased abundance of resident birds was associated with increased abundance of breeding migrants, however. This pattern was found not only in the foliage gleaning guild but also with all passerine birds, indicating that food was not an important contributor to this pattern. We elaborate a hypothesis suggesting heterospecific attraction in northern breeding bird assemblages. Habitat generalist migrants may use the presence of residents as an indicator of safe and/or productive breeding sites in northern unpredictable circumstances.     

Do major host shifts spark diversification in butterflies?

The Escape and Radiate Hypothesis posits that herbivorous insects and their host plants diversify through antagonistic coevolutionary adaptive radiation. For more than 50 years, it has inspired predictions about herbivorous insect macro‐evolution, but only recently have the resources begun to fall into place for rigorous testing of those predictions. Here, with comparative phylogenetic analyses of nymphalid butterflies, we test two of these predictions: that major host switches tend to increase species diversification and that such increases will be proportional to the scope of ecological opportunity afforded by a particular novel host association. We find that by and large the effect of major host‐use changes on butterfly diversity is the opposite of what was predicted; although it appears that the evolution of a few novel host associations can cause short‐term bursts of speciation, in general, major changes in host use tend to be linked to significant long‐term decreases in butterfly species richness.     

Do Stomata Respond to CO(2) Concentrations Other than Intercellular?

Most studies on stomatal responses to CO₂ assume that guard cells respond only to intercellular CO₂ concentration and are insensitive to the CO₂ concentrations in the pore and outside the leaf. If stomata are sensitive to the CO₂ concentration at the surface of the leaf or in the stomatal pore, the stomatal response to intercellular CO₂ concentration will be incorrect for a `normally' operating leaf (where ambient CO₂ concentration is a constant). In this study asymmetric CO₂ concentrations for the two surfaces of amphistomatous leaves were used to vary intercellular and leaf surface CO₂ concentrations independently in Xanthium strumarium L. and Helianthus annuus L. The response of stomata to intercellular CO₂ concentration when the concentration at the leaf surface was held constant was found to be the same as the response when the surface concentration was varied. In addition, stomata did not respond to changes in leaf surface CO₂ concentration when the intercellular concentration for that surface was held constant. It is concluded that stomata respond to intercellular CO₂ concentration and are insensitive to the CO₂ concentration at the surface of the leaf and in the stomatal pore.     

Making the Baruya great again: From glorified great men to modern suffering subjects?

This paper explores avenues for prestige‐making now available to and championed by the Baruya, the archetypal ‘Great Man’ people of Papua New Guinea, who I recently studied following previous work by Maurice Godelier. Amid critiques by Robbins and Ortner of anthropologists’ drive to document and empathise with “suffering subjects”, I suggest that being ‘left behind’ and ‘forgotten’ is an important part of Baruya social life that reinterprets previous ways of ‘making great men.’ Baruya exposure to material and institutional modernity remains very limited. Local rhetorics of being ‘last place’ (las ples) are both concomitant and discordant with Baruya assumptions and assertions of being ‘the greatest people’ of their region. Unable to revive traditional contexts for producing great men through warriorship, shamanism, cassowary hunting, and salt‐making, Baruya turn to the very modernity they cannot quite reach for their own pursuit of masculinity and prestige—which paradoxically now lies within domains also open to women. Desirous to both establish continuity with their glorified past and to depart from it, Baruya's local modernity itself constrains their newly‐shaped desire for prestige—and dramatically changes gender relations in the process. Though the concrete impossibility to ‘be great’ reinforces Baruya perceptions of enduring what we might call a ‘suffering slot’, the larger issue is how concrete experiences sediment into socio‐cultural change over time. This process is informed by a tension between a quest for modernity and its larger failure, resulting in a drive to reignite longer standing values of morality, spirituality, and ultimately, greatmanship.     

Alcodemia: are we training our students to be great thinkers or great drinkers?

Academia has fostered an unhealthy relationship with alcohol that has an undeniable impact on the health and behaviour of students and staff. Subject Categories: S&S: History & Philosophy of Science, Chemical Biology, S&S: Ethics

University life has a lot to offer. And, for better or worse, much of it goes hand in hand with a bottle. Believe it or not, I was a bit of teetotaler in my undergraduate days but quickly made up for it in graduate school, where each celebration included inebriation. Indeed, my initial tour of the laboratory I eventually worked in included a refreshing visit to the grad club. Orientation week ended with a marathon beer blitz at a nightclub. The semester’s first invited seminar speaker was welcomed with the sounds of loose change, ice buckets and the clickity‐clack of organic microbrews being opened. Our inaugural genome evolution journal club was such a success that we vowed to spill even more red wine onto our notebooks the following week. In hindsight, I should have realized at this early stage in my studies that I was fostering an unhealthy and unsustainable relationship between biology and booze. Unfortunately, my post‐graduate education in alcohol didn’t stop there.Like many keen students, I arrived at my first scientific conference with a belly full of nerves and a fistful of drink tickets, which I quickly put to good use at the poster session. The successful completion of my PhD proposal assessment was met with pats on the back as I was swiftly marched off to a local pub with no chance of escape. My first peer‐reviewed paper literally arrived with a pop as Champagne was generously poured into plastic cups for the entire laboratory group. My failures, too, were greeted with a liberal dose of ethanol. “Sorry you came up short on that scholarship application, Smitty. It’s nothing a little weapons‐grade Chianti won’t cure.” “That experiment failed again! Come on, let me buy you a lunchtime martini to make up for it.” Soon I learnt that every academic event, achievement or ailment, no matter how big or small, could be appropriately paired with beer, wine or spirit. Missing from the menu were two crucial ingredients for any burgeoning researcher: moderation and mindfulness.But it was the older vintages that really inspired me – the legendary drinking escapades of my scientific mentors, advisors and idols. The tale of professor so‐and‐so who at that epic meeting in 1993 polished off an entire magnum of rosé at dinner and then went on to deliver among the greatest keynote lectures on record at 9 am the following morning. That celebrated chaired researcher who kept the single malt next to the pipette tips for quick and easy access. The grizzled evolutionary ecologist who never went into the field without half a dozen cans of high‐end smoked oysters and two hip flaks, which didn’t contain water. And so, when I was told by someone in the know of how the most famous geneticist on campus wrote that monumental Nature paper (the one I’d read ten times!) while locked in his office for twelve hours with a six‐pack, I bought into the romance hook, line and sinker. The result: I’ve been nursing a recurring headache for nearly two decades and I’m still waiting on that Nature paper. Most importantly, I now realize the various dangers of romanticizing the bottle, especially for individuals in mentorship positions.Like my idols before me, I’ve accrued a cask full of well‐oaked academic drinking stories, except that they haven’t aged well. There is that heroic evening of intense scotch‐fueled scientific discussion, which led to me forfeiting two front teeth to the concrete sidewalk (my mother still thinks it was a squash accident). Or that time I commemorated the end of a great conference in Barcelona by throwing up on the front window of a café while the most prominent minds in my field sipped aperitifs inside (thank god this was before Twitter). Even more romantic: me buying a bottle of Cotes de Nuits Burgundy at Calgary airport on route to a job interview, discreetly opening the bottle in‐flight because economy class wine sucks, and then being met by airport security upon landing. Let’s just say I didn’t get the job. To some, these anecdotes might seem light‐hearted or silly, but they are actually rather sad and underscore the seriousness of substance abuse. Many readers will have their own complicated experiences with alcohol in academia and, I believe, will agree that it is high time we asked ourselves: are we training our graduate students to be great thinkers or great drinkers? Moreover, this question does not address the equally if not more serious issue of excessive drinking among undergraduate students.As I sit at my desk writing this, I think to myself: is it normal that within a two‐minute walk of my university office there are three different places on campus that I can have a beer before lunch, not including the minifridge behind my desk? Is it normal that in my department the first thing we do after a student defends their thesis is go to the grad club where they can have any alcoholic drink of their choosing for free from the goblet of knowledge, which is kept on a pedestal behind the bar? Is it normal that before the COVID pandemic when I was visiting a prominent university for an invited talk, one of the professors I met with offered me a glass of expensive Japanese gin at 11 am in the morning? (And, yes, I accepted the drink.)Of course, if you don’t want to drink you can just say no. But we are learning more and more how institutional cultures – “the deeply embedded patterns of organisational behaviour and the shared values, assumptions, beliefs or ideologies that members have about their organisation or its work” (Peterson & Spencer, 1991) – can have powerful effects on behaviour. Excessive alcohol consumption is undeniably an aspect of collegial culture, one that is having major impacts on the health and behaviour of students and staff, and one that I’ve been an active participant in for far too long. I’ll be turning forty in a few months and I have to face the fact that I’ve already drunk enough alcohol for two lifetimes, and not one drop of it has made me a better scientist, teacher or mentor. The question remains: how much more juice can I squeeze into this forty‐year‐old pickled lemon? Well, cheers to that.