Time Budgets and Territory Size: Some Simultaneous Optimization Models for Energy Maximizers

A set of optimization models in two variables of choice, territorysize and time spent patrolling for intruders, is presented forenergy maximizers. Models vary in the curvilinearity of therelationship between territory circumference and both intrusionrate and cost of expelling a single intruder. Models are analyzedboth with and without constraints; constraints are on processingrate and on the time spent patrolling, feeding and activelydefending. The models all include the concept of "intruder equilibrium,"an equilibrial density of intruders in a territory resultingfrom a balance between intrusion rate and expulsion by the defender.This equilibrial density can be considered a measure of territorialexclusiveness. The two-variable models predict effects on territory size andpatrol time of variation in food density, intrusion rate, costsof expelling a single intruder in energy and time, food-consumptionrate of an intruder, area of detection while patrolling, totaltime available for territorial and feeding activities, timeto eat a unit of food energy, energy cost of patrol per time,and processing-rate capacity. With increasing intruder rate,optimal territory size usually decreases, whereas optimal patroltime behaves much more irregularly. With increasing food density,optimal patrol time usually decreases, whereas optimal territorysize behaves irregularly. In particular, when intrusion rateand expulsion costs accelerate sufficiently with increasingterritory size and no constraints exist, the higher the fooddensity the smaller the optimal territory size. When food densityis large enough for a constraint to be effective, the oppositerelation can hold and will always hold for a processing constraint. When a particular parameter changes, optimal territory sizeand optimal patrol time may covary or one may increase whilethe other decreases, depending on the parameter and model. A new set of one-variable models is suggested by the two-variablemodels; models optimizing patrol time while holding territorysize constant could correspond to a tightly packed system ofterritories initially determined by settlement patterns. A unifiedonevariable analysis suggests that how food density affectsterritory size when patrol time is constant depends upon whethera constraint is operating: Provided that invasion rate doesnot vary with density of intruders on the territory, time minimizersand constrained energy maximizers decrease territory size withincreasing food density; unconstrained energy maximizers dothe opposite. The addition of a second optimization variable to a one-variablemodel can change qualitative predictions about variation inparticular parameters (e.g., food density) and can increasethe number of parameters predicted to affect optimal territorysize and patrol time.     

Determinants of territory size in the pomacentrid reef fish,Parma victoriae

Summary Factors governing the size of territories defended by the pomacentrid reef fish, Parma victoriae, were investigated, prompted by contradictory predictions in the literature concerning the effects of food supply and competitors. Observations were carried out over the non-breeding period (March–October) on a medium density population in which territories were partially contiguous. The territory size of adult fish varied between 3 and 26 m², and was inversely correlated with local densities of conspecifics. The same range in territory size was found for both males and females, which did not differ in the time they spent on territory defence and foraging activities. No correlation existed between territory size and the abundance of algal food, body size, age or time spent on territory defence. Also, there was little variation in territory size over time, despite seasonal changes in the abundance of food algae.Experimental reduction of food supplies on isolated territories of males and females had no effect on territory size. In a higher density habitat an experiment was carried out in which population density and food abundance were simultaneously manipulated. This showed that territory size was primarily determined by intraspecific interactions, as territories exhibited considerable increases in size upon removal of neighbours. No changes in the size of defended areas resulted from either artificial increases or decreases of food levels. There were also no changes in the time spent on defence of territories, foraging time or feeding rates associated with food manipulations or territory expansion, which suggested that food was not a limited resource. This conflicted with current theories proposed to explain territory defence and expansion. It is hypothesized that intraspecific interactions constrain territory size well below the optimum in terms of the abundance of preferred food algal species.     

Cost of territory establishment in hummingbirds

Summary Time spent in territorial defense was measured during territory establishment for non-breeding Black-chinned (Archilochus alexandri) and Anna's (Calypte anna) hummingbirds. Newly established territory holders spent more time chasing intruders than neighboring established owners, which served as controls. This higher investment in defense by the new owners was due to 1) a longer time spent per each chase and 2) in some cases, a higher frequency of chases at the onset of territory ownership.     

秦岭川金丝猴冬季和春季在自然栖息地的空间利用

2000年9月到2003年3月共计197天的时间里,我们采用目标动物取样法(Focalanimalsampling)和行为的全事件记录法(Alloccurrencesampling)对一群生活在秦岭北坡周至保护区内的秦岭金丝猴(Rhinopithecusroxellana)在自然栖息地内空间利用的进行了研究。当猴群在离开人工投食区进行自由活动时我们开始收集数据。结果表明:秦岭川金丝猴在不同年龄性别组的个体对植被的空间利用明显不同,它们花费每天活动的14%的时间在地面上活动,53%时间在树叉处活动,33%的时间在树冠中间活动。与其它年龄性别个体相比,成年雄性有27%的观察时间在地上活动,并且20%的取食时间或29%的休息时间是在地上的,明显地高于其它年龄性别组的个体。群体迁移时,成年雄性有53%的时间在地上移动,而只有13%的时间是在树冠层移动的。在通过不同树冠的时候,成年雄性经常会同时抓住两边再把身体摆过去。它们也经常下到地上迁移而回避在树间跳跃。相比之下,亚成年雌性和青少年猴更加经常地在低植被层和树冠层中找食和休息。它们明显地比成年猴更加频繁地在树冠中移动,却很少下地。它们还经常使用跳跃的方式通过树冠间的空隙。从观察到摔下树的事例分析,青少年猴从树上摔下来的风险比成年猴大。本文进而讨论了影响秦岭金丝猴空间分布和移动的因素,比如说身体的重量等.     

Extraterritorial forays and male parental care in hooded warblers

Extrapair paternity is common among many songbird species yet few studies have quantified male extraterritorial foray (ETF) effort and examined potential trade-offs. One potentially important constraint for males is the need to provide parental care. Current models of male extrapair mating tactics propose that males reduce extraterritorial foray effort later in the breeding season because they face a trade-off between feeding nestlings versus pursuing extrapair matings. However, detailed field studies examining the trade-off between paternal care and male extraterritorial forays are lacking. We used radiotelemetry to quantify male extraterritorial foray effort in hooded warblers, Wilsonia citrina, to test the widely held predictions that: (1) males make significantly fewer and shorter forays during the nestling stage relative to other stages (i.e. fertile and incubating stages); and (2) male extraterritorial foray effort is negatively correlated with parental effort. Males made 0.87+/-0.09 forays/h and spent on average 12.2% of their time foraying off territory. Results were equivocal; some data suggested male foray effort decreased in relation to parental care, while other data suggested otherwise. Pairwise tests controlling for (1) extrapair mating opportunity among males and (2) male, territory and social mate quality revealed a possible trade-off between the mean duration and percentage of time in extraterritorial foray versus providing parental care. Conversely, results also revealed (1) no difference in foray rate, foray duration or percentage of time spent off territory over the various stages of the breeding season, (2) no relationship between male foray effort and male feeding rate, and (3) no difference in foray rate in pairwise comparisons, controlling for variability in extrapair mating opportunity and male quality. Overall, the trade-off between providing male parental care and pursuing alternative mating tactics may not be as strong for male hooded warblers as once hypothesized because males dedicated relatively little time to seeking extrapair copulations off territory. Copyright 2000 The Association for the Study of Animal Behaviour.     

Interspecific assistance: fiddler crabs help heterospecific neighbours in territory defence

Theory predicts that territory owners will help established neighbours to repel intruders, when doing so is less costly than renegotiating boundaries with successful usurpers of neighbouring territories. Here, we show for the first time, to our knowledge, cooperative territory defence between heterospecific male neighbours in the fiddler crabs Uca elegans and Uca mjoebergi. We show experimentally that resident U. elegans were equally likely to help a smaller U. mjoebergi or U. elegans neighbour during simulated intrusions by intermediate sized U. elegans males (50% of cases for both). Helping was, however, significantly less likely to occur when the intruder was a U. mjoebergi male (only 15% of cases).     

Behavioural time budget of breeding king penguins (Aptenodytes patagonica)

As do so many other seabirds, penguins fast when ashore for breeding. For penguins in dense colonies, territory defence seems to imply conflicting energetic requirements because of its assumed high energy cost, when the birds need to limit energy expenditure to cope with their fast. In this context, behavioural time budget over 24 h was investigated during breeding in the king penguin, Aptenodytes putugonicu , by using a remote-controlled videocamera. The comparison of day-night activity was performed in relation to breeding status (incubation vs. brooding) and duration of fasting (beginning vs. end of incubation shift). Five categories of behaviours were quantified: territoly defence, comfort, resting, sleeping and chick-feeding. Breeding king penguins remain active by day as well as by night. Between incubation and brooding we found a three-fold increase in the energy consuming temtory defence, together with a drastic decrease in that posture which corresponds to deep sleep, is. when most energy is saved. These increases in aggressiveness and vigilance may be related to protection of the newly hatched chick. Between the onset and the end of an incubation shift, the time spent in sleep increases three-fold, whereas territory defence remains unchanged. These data for penguins under natural conditions accord with previous studies on captive birds which have shown that an increasing proportion of sleep during the course of fasting may contribute to energy saving. On the other hand, both resting (which is the main component of penguins'time budget; about 65%) and comfort (about 16% of time) show no change either between incubation and brooding or during the course of fasting.     

Competing Females and Caring Males. Polyandry and Sex-Role Reversal in African Black Coucals, Centropus grillii

Most species of birds show bi‐parental or female‐only care. However, a minority of species is polyandrous and expresses male‐only care. So far, such reversals in sex roles have been demonstrated only in precocial bird species, but there was suggestive evidence that such a mating system may occur in one altricial bird species, the black coucal, Centropus grillii. In a field study in Tanzania we investigated whether black coucals are sex‐role reversed and polyandrous. We found that males were mated to one female, rarely vocalized and provided all parental care from incubation of eggs to feeding of young. In contrast, female black coucals were about 69% heavier and 39% larger than males and polyandrous. They spent a large proportion of time calling from conspicuous perches, defended breeding territories, did not help in provisioning young and had a higher potential reproductive rate than males. We conclude that the black coucal currently represents the only altricial bird species with sole male parental care and a classical polyandrous mating system. High nest predation pressure and small territory sizes due to high food abundance may have been important factors in the evolution of sex‐role reversal and polyandry in this species.     

The Consequences of Predation Risk on the Male Territorial Behavior in a Solitary Bee

Territorial males may adopt a mating tactic that yields greater reproductive success but that at the same time increases the risk of predation. Plasticity in reproductive behavior can reflect a balance between sexual selection and natural selection. In this study, we sought to verify the effect of predation risk on territorial behavior of males of the solitary bee Ptilothrix fructifera (Apidae). Males of the species employ alternative mating tactics and can be territorial in defense of larval food sources. By manipulating predator models in the field, we tested whether (1) males avoid perch flowers containing predator models; (2) males alternate between mating tactics when their territory is associated with a predation risk; and (3) female foraging on flowers in a territory is altered in the presence of a predator model. We measured the responses of males and females in flowers containing and not containing a model of a spider or a stuffed bird. The results show that territorial males of P. fructifera alter their territorial behavior when faced with a high risk of predation. They do not abandon their territory or change to a non‐territorial mating tactic, but instead change the use of their territory, avoiding flowers containing predator models or perching on other flowers when the previous flower presented a potential predation risk. Female P. fructifera decreases the frequency of their visits to flowers and the length of time spent there in the presence of a spider model. In short, in the face of predation risk, females and males alter their behaviors at the cost of less efficient foraging and searching for partners, respectively.     

Maternal investment and reproductive success in Chinese water deer

Among cervids, maternal investment, estimated as the amount of resources and care allocated to the offspring, was expected to be related to species body size. Therefore, maternal investment in a herd of captive Chinese water deer Hydropotes inermis, a relatively small species of cervid, was investigated over 3 years. Except during the lactation period, reproductive females spent about 2-fold more time resting than feeding. During lactation, the amount of time spent feeding increased highly (25.3 min/h during lactation vs 17.3 min/h during the gestation period). Females spent less than 30% of time in communal behaviours with offspring. They did not reject alien fawns during this care period. Frequency and duration of suckling events decreased exponentially from the second week onwards. More than 10% of suckling bouts were non-filial. Prenatal investment leads to a mean litter mass (about 12% of maternal mass) higher than in most cervid species. Postnatal investment in fawns represents a daily mass gain of ca. 85 g/d during the first 2 weeks, without any sexual difference. Female production, timing and synchrony of births and survival of fawns characterized reproductive success. Seventy percent of mature females gave birth, with a mean of 1.9 offspring per female. The sex ratio was even. Births were synchronous, 80% of births occurring in 25 days. In this herd, 0.74 fawn per female was successfully weaned and 0.56 fawn per female survived through their first year. Based on these results we conclude that reproductive strategy of Chinese water deer was efficient and characterized by mother-offspring relationships typical of hiders and high levels of pre- and postnatal investments. This strategy seems typical of small species of cervids without marked sexual dimorphism.[Current Zoology 55(2):102-110,2009].     

Activity budgets of a marked common loon (Gavia immer) nesting population

A newly devised nightlighting technique was used to capture breeding adult common loons (Gavia immer) at the Seney National Wildlife Refuge in northern Michigan in 1989. The behaviors of 6 pairs of known-sex, color-marked common loons were subsequently quantified during the breeding cycle in 1990. Collected observational data indicate that foraging, resting, locomotion, and preening were frequent throughout the breeding cycle. Time spent foraging was greatest during the pre-nesting period (53 to 57%), but declined significantly during the nesting and post-nesting periods (p<0.05). Time spent foraging during the pre-nesting period was similar to that of fall and winter studies. During the pre-nesting period adult loons spent about 15% of the time in locomotion; this was significantly greater than the other time periods (p<0.05) and is attributed to selecting a nest site. During the nesting cycle, almost half of each bird's time spent was nest-sitting. Sexual differences were negligible during nest-sitting. Resting and chick-rearing were the predominant behaviors during the post-nesting period and were responsible for the biggest difference in parental duties. Time spent preening declined from 8% during the pre-nesting period to 4 to 5% during the post-nesting period. Time spent by nesting pairs to produce chicks is approximately 10% during pre-nesting, 48 to 49% during nesting, and between 38 to 44% during post-nesting. By quantifying and establishing behavioral standards, subtle abnormalities or changes can be detected to better manage for viable common loon populations.     

Family-based territoriality vs flocking in wintering common cranes Grus grus

We describe winter territoriality in common cranes, Grus grus , a long-lived migrant species with long-lasting pair bonds and parental care extending throughout the winter. Cranes are territorial in the breeding season, and usually gregarious during migration and wintering. Only 2% of the families present in our study area were territorial, all other families foraged in flocks with immatures and adult pairs. Territorial pairs defended the same winter territory year after year, but only when they had offspring. They were gregarious otherwise. The average breeding success measured throughout several years was higher in territorial pairs. Winter territories were small (0.7 km² on average), but included a higher diversity of habitats than the areas visited by gregarious birds (11.7 km² on average). Adults of territorial families showed longer vigilance times, and lower food intake rates than did adults in flocks, which were compensated with a longer time spent foraging per day. The accumulated daily food intake did not differ between adults in flocks and in families. We suggest that winter territoriality is a facultative strategy, conditioned by parental experience and habitat availability.     

Intertidal territoriality and time-budget of the surgeonfish, Acanthurus lineatus, in American Samoa

Synopsis The herbivorous surgeonfish Acanthurus lineatus aggressively maintained feeding territories in the surf zone of the outer reef flat in American Samoa. Intertidal territories were re-established each morning, as well as after displacement by low tides or rough surf. Day-to-day site fidelity of recognizable individuals was high: 99.9% return rate per day for adults (15–20 cm), 99.6% for juveniles (8–13 cm), and 97.2% for recruits (2.5–5 cm). Fish fed on turf algae primarily in the afternoon (80% of available time), and spent 10% of their time on active territorial defense and 2–13% of their time on forays from their territory. On average, a fish defended its territory 1900 times daily and took 17 000 bites (= 7400 bites m^–2 d^–1), but rough surf reduced feeding by 60% and defense by 75%. High territorial defense requirements significantly reduced feeding rates. Although the distribution and behavior of this species in Samoa was in large part similar to that reported for it elsewhere (Australia, Indian Ocean), there were notable differences: in Samoa A. lineatus densities within colonies were greater (0.4 fish m^–2), territory size was smaller (2.3 m²), and defense rate against intruders was greater (2.5 attacks min^–1). These differences in Samoa may be related to their smaller body size, greater abundance or increased food supply caused by hurricane damage to reefs which has enhanced the algal turfs that A. lineatus feeds upon.     

Do Male Activity Level And Territory Quality Affect Female Association Time in The Brown Anole,Anolis sagrei?

Female mate preference is an important component of sexual selection because some male traits, such as physiology and proficiency in acquiring resources, are indicators of male quality. In lizards, the importance of female choice remains unclear as results reported from previous experiments are contradictory. Here, we investigated the influence of male activity level, its associated physiology, and territory quality on female preference, estimated as association time, for male brown anoles, Anolis sagrei. Male A. sagrei were first rated for endurance then used in mismatched‐pair female association trials. Preference was scored as the time a female spent near a male relative to the amount of time she was in his half of the trial arena, and both male and female behaviors were recorded. Levels of blood glucose were measured in males before and after the endurance tests, and before and after the association trials. Levels of stored glycogen were measured in leg muscle and liver samples collected from males after an association trial. A path analysis indicates that final blood glucose levels affect male activity and that female preference is influenced by male activity. In a second experiment, females were given a choice between a male in a territory supplemented with plants and a size‐matched male in a bare territory. Male activity levels were recorded when both males interacted with the female. In those cases, females spent more time with the more active of the two males, regardless of territory quality. Combined, these results suggest that female A. sagrei exhibit preference for male activity regardless of territory quality.     

Conflicting Territory Use in Males and Females of a Monogamous Ungulate,the Kirk's Dikdik

In monogamous mammals it is often unclear why males do not defend larger territories to attract more than one female. I investigated the territoriality of the monogamous Kirk's dikdik, Madoqua kirki, a dwarf antelope, in which food resources increase with territory size and some males defend enough resources for more than one female. Yet, all males are paired monogamously. When males were removed from small territories, their female partners spent more time outside of their territories than females in large ones. When females were removed, their male partners almost never left. Pairs in small territories spent more time together than pairs in large ones. Paired males left mostly together with their females, apparently not on their own initiative. Presumably because females in small territories left more often, their males spent more time outside in the female's company than males in large territories. I argue that males in smaller territories can keep better track of their females and that they can effectively reduce their females' time outside. Male intrusion pressure was unrelated to territory size, but it increased in the presence of unguarded females. If large territories decrease the ability to mate guard, and if unguarded females attract competing males, then defending large territories may be uneconomical, even it they could attract more than one female. On the other hand, territories must be large enough to satisfy the requirements of a single female.     

Diet of a Group of Callicebus torquatus lugens (Humboldt, 1812) During the Annual Resource Bottleneck in Amazonian Colombia

A group of Callicebus torquatus lugens using a territory of 22.25 ha in eastern Colombia showed a varied diet throughout the annual period of lowest fruit availability. This is a time when the females are usually pregnant. During a 6-month period the study group's diet consisted of 59.4% fruits, 26.9% immature seeds, 6.4% leaves, 3.9% flowers, and 3.4% insects and spiders. At the fruit bottleneck, consumption of seeds and flowers increased, while consumption of leaves and insects showed no particular trend. They ate 62 species of plants: 45 for flesh, 6 for seeds, 2 for flowers, and 13 for foliage. The most important families in terms of species chosen are Moraceae (8 species, or 11 species if Cecropiaceae is included), Myristicaceae (7), Arecaceae (4), Chrysobalanaceae (4), and Euphorbiaceae. The most important families in terms of feeding time are Myristicaceae (25%), Euphorbiaceae (15%), Moraceae (14%), and Arecaceae (9%). Of 440 marked feeding trees in the territory of the group, 41.1% are represented by Sandwithia heterocalyx (Euphorbiaceae). This species is the most important food in the diet and has the highest density of all food trees in the home range. It followed by Heterostemon conjugates (Caesalpiniaceae) (10%), Iryanthera ulei (Myristicaceae) (6.1%), Anaxagorea brachycarpa (Annonaceae) (5.9%), and Iryanthera crassifolia (Myristicaceae) (3.4%). The remaining 33.5% of the marked trees are represented by the other 57 species. In terms of time spent feeding, the important trees in the diet include Sandwithia heterocalyx (13.9%), Virola melinonii (10%), Iryanthera ulei (8.35%), Oenocarpus bataua (7.06%), and Heterostemon conjugates (6.53%). We suggest that Callicebus torquatus should be described as a frugivore–granivore; they share with the Pitheciin an immature seed-eating adaptation.     

Temporal partitioning of a floral resource by territorial hummingbirds

Most studies of territoriality in hummingbirds have focused on intraspecific competition for resources and the consequences for the spatial distribution of individuals within a habitat. As a result, we know little of the effects of interspecific competition for resources and less still of temporal resource partitioning. Here I describe the interactions of four species of tropical hummingbird which defended the same territory at different stages in the flowering period and at different times of the day. The pattern of territory defence was greatly influenced by the dominance hierarchy between species and the costs and benefits of territory ownership. I used a simple economic model to calculate the predicted territory size based on four potential strategies. Hummingbirds appeared to be defending territories of the smallest economical size, agreeing with two hypotheses: (1) that hummingbirds minimize the cost of territory ownership and (2) that hummingbirds maximize the time spent sitting. The model predicted accurately the observed pattern of territory acquisition; hummingbirds initiated defence as soon as the territory contained sufficient resources and were either displaced by a larger species or replaced by a smaller one as the value of the territory changed.     

Seasonal Variation in the Activity Patterns and Time Budgets of <Emphasis Type="Italic">Trachypithecus francoisi</Emphasis> in the Nonggang Nature Reserve,China

Activity patterns and time budgets are 2 important aspects of animal behavior that researchers use to investigate ecological influences on individual behavior. We collected data on activity patterns and time budgets in 1 group of François’ langurs (Trachypithecus francoisi) from August 2003 to July 2004 in the Nonggang Nature Reserve, Guangxi Province, China, via instantaneous scan sampling method with 15-min intervals. The diurnal activity pattern of François’ langurs showed morning and afternoon feeding peaks, with a midday resting peak. Seasonal change was apparent in the activity pattern: 2 significant feeding peaks occurred in the dry season and only 1 significant feeding peak in the rainy season. The group spent an average of 51.5% of the daytime resting. Feeding and moving accounted on average for 23.1% and 17.3% of the activity budget, respectively. Subjects spent little time on social activities, averaging 2% for grooming and 5.5% for playing. Their time budgets showed significant seasonal variation: they spent a greater proportion of time on feeding and less time on resting and grooming in the dry season than in the rainy season. They also differed among different sex-age classes: immatures spent more time playing, whereas adults devoted more time to resting, feeding, and grooming. Correlations between time budgets and food items or food availability clearly indicated that François’ langurs might adopt an energy-maximizing strategy when preferred foods were scarce in the dry season.     

Effects of behavioural time budgets and nest-building efficiency on male reproductive performance in red bishops ( Euplectes orix )

In this study we have investigated the effect of nest-building behaviour, courtship behaviour, and male–male interactions on male reproductive performance of the red bishop (Euplectes orix), a highly polygynous, colonially breeding weaverbird species. Previous studies on red bishops have revealed that male reproductive success is mainly determined by the number of nests built in a territory, and that reproductive success and the number of nests both vary substantially among males. Here we test whether the high variation observed in reproductive performance is related to male behavioural patterns (as assessed by time-budget analysis) and/or nest-building efficiency (as assessed by the number of fibres incorporated in the nest in unit time). We collected data on male time budgets and analysed behavioural patterns for three breeding seasons. A greater number of nests built was positively related to both the amount of time allocated to nest-building behaviour and the efficiency of nest building. Neither the amount of time spent in courtship behaviour nor the amount of time spent in male–male interactions was related to reproductive success. Male reproductive success, irrespective of the number of nests built, was partly determined by the number of fibres incorporated, suggesting some importance of nest quality in terms of nest chamber density to male reproductive success. There were no trade-offs with regard to time allocated to different behaviour. Instead, males differed with regard to their territory attendance and activity levels, which might be because of differences in energy resources and may thus reflect inherent differences in male body condition and, ultimately, male genetic quality.     

灰喜鹊的行为生态学研究Ⅰ．生殖行为

在从南到北的地理分布上,灰喜鹊的繁殖期相应有所推迟。在它们的繁殖区域,人类的影响越大,其巢也建得越高、越隐蔽。这种很强的适应性使得它们在城区和近郊区能够更好地生存和繁殖。北京地区的灰喜鹊在4月中、下旬开始建巢,5月底是产卵高峰期。在孵卵期它们不断地翻动卵,以使其受热均匀。灰喜鹊对卵的数量比对卵的颜色和大小更敏感。孵卵期约15-17天,幼鸟18-20天出巢。在北京大学校园内的灰喜鹊的繁殖成功率约为69.05%.建立了灰喜鹊的发育行为谱。在繁殖期,灰喜鹊的巢彼此靠得较近,形成一个集体生殖领域,共同进行集体防御。