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Global warming has the potential to affect many animal species, in particular temperature-dependent insects with their short generation times and high reproductive rates which facilitate adaptations to long-term climatic fluctuations. Aphids are the model species in studying the association of insect biology with large-scale climate fluctuations because they multiply only within a certain range of temperatures and their rate of development directly depends on temperature. Here, we investigate the effect of climate warming on phenology and voltinism of the juniper aphid (Cinara juniperi De Geer 1773), a native species of a temperate climate zone in Poland. We also experimentally test for the temperature optimum of the study species. Our study demonstrated that environmental conditions significantly affected phenology of juniper aphid. The timing of larval emergence depended on mean temperatures in March, and in warmer years larvae appeared earlier. The emergence of the sexual generation was related to mean...

Nest predation is a major source of reproductive failure in birds and thus it can exert selection on both parental and offspring strategies. Begging calls are known to be a powerful component of parent–offspring communication but these calls can also increase predation risk. Here we demonstrate a sophisticated strategy for the development of begging vocalization in a species under high nest predation. Blackcap Sylvia atricapilla nestlings spend most of their nesting period silent, and develop begging calls just before they are able to fledge. The onset of begging vocalization matches the onset of endothermy, which enables Blackcap chicks to leave the nest. We demonstrate experimentally that begging calls function as a signal of the increased needs of homeothermic nestlings. Playback of begging calls conducted in nests with silent nestlings resulted in a significant increase in feeding rates and a decrease in brooding. Development of begging calls only at the age of endothermy allows species under high nest predation to keep the risky period of begging vocalizations and frequent feeding to a minimum. This strategy may constitute an evolutionary solution to high predation pressure in some open nesting passerines. This is the first study to demonstrate the existence of silent begging in a passerine.

Ant-aphid mutualism has been investigated by many authors but it is unknown if anti-predator protection provided by ants is the main benefit for aphids. The aim of our paper is to analyse the ant-aphid interactions in the absence of predators. Based on video recordings we distinguish ant behaviours in interactions with attended aphids and we present ant time-budget at different times of the day. We also test if an aphid colony can survive without ant attendance in an environment free from predators and we inquire how much ant attendance is needed to maintain an aphid colony in good condition. Our study shows that, despite the lack of predation pressure, aphids of the species Cinara tujafilina were not able to survive without ant attendance and the extinction was caused by the excessive honeydew that covered aphids and their surroundings. We also found that ants cleaning aphids was the most frequent and time-consuming activity in ant-aphid interactions. However, in general, ants interacted with aphids only...

We studied the effect of ectoparasitism by hematophagous larvae of the blow fly of the genus Protocalliphora on nestling blackcaps Sylvia atricapilla in southeast Poland. Approximately 81% of blackcap nests left by nestlings contained Protocalliphora larvae; however, mean parasite load was only 1.8 larvae per nestling. Nestling mass and tarsus length measured just before fledging did not differ significantly with parasite load. This finding might have resulted from several factors. First, the number of larvae per nestling was very low, which may be connected with the structure of blackcap nests. Second, the time of exposure of nestlings to parasitic larvae in the studied species is relatively short as fledglings are able to leave a nest when they are 9 days old. The combination of the open lacework structure of blackcap nest and a very short nestling period may constitute an evolutionary adaptation that enables blackcap nestlings to escape the cost of Protocalliphora parasitism.

Nestling development is among the most energy-demanding periods of a bird’s lifetime and altricial species require extensive parental energy investment in the form of feeding and heating. In the present study I analyze the relation and trade-offs between nestling growth, development of thermoregulation and feeding rate in blackcap Sylvia atricapilla, a species suffering from high nest predation. Nestlings were characterized by rapid growth but they achieved only 80% of adult mass prior to fledging. Body mass showed highest relative growth rate before nestlings achieved homeothermy. The onset of endothermy, indicated in day 7, coincided with 90% of nestling fledgling weight, indicating that the two processes are separated in time. A strong negative correlation between feeding rate and growth rate demonstrates that blackcap nestlings develop their bodies under relatively low feeding rates and more feeding is needed for maintenance of body temperature than for body growth. The study indicates high cost of endothermy for parents – endothermic nestlings received over 100% more feedings than ectothermic ones. The findings are discussed in the light of adaptation of the species to high predation risk.

In the present study we test the ability of insight (solving novel problems) in a small passerine. Our paper reports on the predation of Blackcap Sylvia atricapilla nestlings by the Spanish Slug Arion lusitanicus and the reaction of bird parents to a novel predator. The Spanish slug is an invasive pest species, first documented in the study area in recent years. We examine whether parents are able to recognise a new species as a danger to their young and counteract to nest failure by removing a slug. We also inquire whether parents can instantly recognise that a chick is dead from watching its injuries and a slug feeding on it. Finally, we analyse if the recognition that nestlings are dead comes along with parent's understanding of losing a brood. The most striking result of our study is that none of Blackcap parents reacted aggressively against a predator that was absolutely harmless to adults and small enough to be removed from a nest. We also describe other irrational behaviours like incubating dead ch...

Among various begging stimuli, mouth coloration has received increasing attention in recent years, and previous research has demonstrated that mouths of nestling Canaries Serinus canaria get redder with the extent of food deprivation and that parents preferentially feed nestlings of redder gapes. This study assesses whether the intensity of red mouth colour in nestling Blackcaps Sylvia atricapilla is a signal in parent–offspring communication. This is one of the few species with a naturally red gape in which the function of mouth redness has been tested. Three predictions were experimentally tested: (1) reddening the gape of a single nestling within a brood increases its provisioning in relation to other siblings; (2) reddening the gapes of all nestlings within a brood increases parental feeding rate; and (3) food deprivation increases nestling mouth redness. The effect of nestling quality on mouth redness was also assessed. The intensity of gape coloration affected food distribution, but in a way opposite to that expected: an increase in mouth redness of the nestling caused reduced feeding by parents. However, reddening the gapes of all nestlings had no effect on provisioning of the whole brood, suggesting that Blackcap parents use different cues for provisioning particular nestlings and the whole brood. Intensity of mouth redness in Blackcap nestlings was not affected either by food deprivation or by nestling quality in terms of mass and rank in the nest.

Development during the relatively short time that young spend in the nest is crucial in a bird's life history. The rate of nestling growth strongly depends on numerous environmental and social factors, even within the same species or population. In the present study I examine the relative contributions of brood size, hatching asynchrony, hatching date and feeding rate in determining intraspecific variation in the growth of Eurasian Blackcap Sylvia atricapilla nestlings. I found a significant effect of brood size, hatching order and date on nestling development. However, the effect of hatching order and date was significant only for young nestlings and it gradually disappeared with nestling age. The only factor significantly affecting nestling development just before fledging was brood size. Nests of four siblings produced the heaviest young with the longest tarsi. This probably resulted from the highest feeding rate per nestling observed in broods of four nestlings. The study shows that for Blackcaps bree...

We analysed the eggs of the European starling Sturnus vulgaris for variability of UV and blue-green colouration. We noted the calcium deposition in eggshells, egg measurements, light conditions in nests and starling eye properties. Egg colouration shows high within-clutch similarity. Intensity of the blue-green egg colour neither depends on Ca deposition in the eggshell nor correlates with egg measurements, clutch size and laying date. This suggests that the intensity of the blue-green colour of starling eggs does not reflect female condition, which is reported to affect egg and clutch parameters. Low light intensity in cavities enables only mesopic vision, which is characterised by degraded visual acuity and colour sense, as well as Purkinje shift. As a consequence, the probability of precise assessment of the differences in eggs colour by starling males, crucial for the signalling hypothesis (Moreno & Osorno 2003), is not high. On the other hand, irrespective of its intensity, blue-green is the last col...

The great reed warbler, Acrocephalus arundinaceus, is one of the most intensively studied species in the area of vocal behaviour and an important model in studies of sexual selection. We evaluated performance of the whistles produced by different males and examined whether individuals improved their performance over consecutive seasons. Finally, we tested whether the performance of whistles reflected males’ philopatry and harem size. We assessed whistle performance based on duration and consistency. Our analyses showed that great reed warbler males improved the performance of their whistles in subsequent seasons. Whistles became both longer and more consistent from one year to the next. We also found that males’ harem size was significantly related to whistle performance, which in turn reflected philopatry. Subsequent analyses revealed that the performances of polygynous and philopatric males differed significantly from those of monogamous, unpaired and new males. As philopatry is preferred by great reed warbler females, it is in the males’ interest to advertise this feature. Coding philopatry in the songs of individual males seems to be an easy and efficient way of informing females about males’ familiarity with the breeding grounds. The proper performance of difficult double-element whistles, the mastery of which may be time consuming, seems to be a good candidate for indicating males’ philopatry. If so, the quality of whistle syllables may also reflect differences in the general quality of individual males as high performance levels may be associated with both males’ longevity and their ability to learn.