European pied flycatcher

The male mating behavior has two key characteristics: desertion of the primary female and polyterritoriality. The males travel large distances, an average of 200–3,500 metres (660–11,480 ft), to find his second mate. After breeding with the secondary female, the males return to their first mate. The males of this species are polyterritorial; the males will acquire multiple nest sites to attract a female. Upon breeding with this first female, the male will procure more nesting sites, typically some distance from the site of the primary female, in order to attract a second female for mating. The males that have better success at polygyny are typically larger, older and more experienced at arriving earlier to the mating sites.[13]

Polygyny threshold model graph

The female behaviour has also been studied in depth, especially due to the fact that some females accept polygyny while others are able to maintain monogamous relationships. The first female in a polygynous relationship does not suffer much in comparison to females in monogamous situations. These primary females gain greater reproductive success because they are able to secure full-time help from the male once he returns from his search for a second mate. The second female, however, often suffers from polygyny. These females have 60% less offspring than females that are in a monogamous relationship.[14] These findings are consistent with the polygyny threshold model, which is depicted at the right. Additionally, the secondary female lays a smaller clutch which she is more likely to be able to rear on her own.

Another behavior that is relatively frequent in European pied flycatchers is the practice of extra-pair copulations (EPC). Thus, the male practicing EPC will have a group of offspring raised successfully without any parental investment on his part. The female may benefit from EPC if the second male is judged to have superior genes to the original male. Another benefit that EPC adds is that there is an increase in genetic variability. However, females are not typically very welcoming of EPC. A female that is being pursued for an EPC will either passively allow the male to copulate with her, or will resist it and risk injury due to the male's aggression.[15]

In an experiment conducted from 1948 to 1964 in the Forest of Dean in Gloucestershire, two hundred and fifty nest boxes were carefully recorded for their locations and then analyzed for their inhabitance.[16] The median breeding dispersal (the distance between successive nests) of the European pied flycatcher ranges from about 52–133 metres (171–436 ft), with the average distance between nest sites being about 45 metres (148 ft). This distance typically depended on the breeding density in each year. The study found little evidence to suggest a difference in breeding dispersal between years or between monogamous and polygynous males. As a result, the data for the separate categories could be combined. The breeding dispersal over longer distances could result in both mate fidelity as well as mate change, the latter of which occurs either while the previous mate is still alive, or following the death of the mate. The breeding dispersal distances of birds that survive more than three breeding seasons were studied, and the results showed that the site fidelity increased with more successive breeding attempts. The same long-term study also found that older European pied flycatchers, both male and female, were more likely to move shorter distances between breeding seasons than younger birds were. When mates were observed to re-establish their pair bond, they tended to occupy certain areas that were near the nest site established in the previous breeding season. In addition, female birds were less likely to return to a former breeding site following the death of, or divorce from, their former partner. When a pair divorces, the females have been observed to move greater distances away than the males. As a result, females that keep the same mates from year to year end up moving shorter distances for each mating period than those that divorce. Divorce has little influence on the likelihood of males moving away from their original nest site. The study found that males that keep the same mate do not move significantly smaller distances than males that divorce.[16]

Since most bird species exhibit monogamous mating behaviors, the polygynous behavior of the European pied flycatcher has sparked much research. There are three main hypotheses that seek to explain why females settle polygynously when it lowers their overall fitness and reproductive success compared to a monogamous relationship.[17]

Adult male in Finland

Adult female in Finland

The first hypothesis is the "sexy son" hypothesis which asserts that although females experience an initial reproductive loss with their first generation, the reproductive success of the second generation compensates for the initial loss. The second generation of males is thought to be privileged because it will inherit the increased mating ability, or attractiveness, from their fathers and thus will have high success in procuring mates upon maturation. Since these "sexy sons" are projected to have heightened reproductive success, the secondary female's reproductive success in turn improves.[18] Some researchers, however, have refuted this theory, stating that offspring born to secondary females suffered from poor nutrition, which resulted in shorter tarsi and lower weights than the progeny of primary and monogamous females. These phenotypic traits contribute to lesser success in mate acquisition, rejecting the "sexy son" hypothesis.[12]

The second hypothesis claims that deception from the male flycatcher explains a female's choice to mate with an already-mated male despite the relative decrease in reproductive success.[13] The deception arises from the polyterritoriality of the males, meaning that the males are able to deceive the females through the use of separate territories. This hypothesis attempts to describe why males have developed polyterritorial behavior. The typical long distances between nest sites suggest that males acquire multiple nest sites to facilitate the deception of the secondary female.[12] A study showed that females leave the male upon discovering that he is already mated, as long as she discovers this fact before laying season.[13] However, another experiment with European pied flycatchers in Norway produced results that refute the deception hypothesis.[19] The secondary female birds in their study raised larger clutches than primary females. The study also showed that deception is not an evolutionarily stable strategy for males, because secondary females would notice the frequent visits to the primary females and then elect to choose another mate. According to the deception hypothesis, already-mated males display polyterritorial behavior that increases their chances of acquiring another mate. Unmated males were shown to display mating behavior, consisting mostly of singing, at their nest site. On the other hand, already-mated males would need to disrupt their singing at their secondary territories in order to return to their primary nest. This can occur both before and after the time of their second mating.[20] As a result, it decreases the chance that females would be deceived, leading to an evolutionarily unstable strategy.[21]

Adult female at the Kochelsee, Schlehdorf, Germany

The third hypothesis asserts that females settle for polygyny because it is hard to find unmated males.[19][22] This theory assumes that there is aggression between females to find mates and asserts that polyterritoriality actually helps to alleviate this aggression, allowing the second female a place to settle and breed peacefully.[23] Although the deception hypothesis suggests that males are more successful at farther secondary territories because they can hide their marital status, the female-female aggression suggests that males occupy distant secondary territories to reduce aggression between the primary and secondary females. Primary females display aggression and prevent other females from settling near the initial nest to ensure that they acquire the male parental care.[24] Primary females were seen in experiments to visit the second territory and behave aggressively towards the secondary female. The number of such visits decreased with increasing distance between the nests. It is also important for the primary female to be able to detect an intruding female as soon as possible, because the longer the intruder has been present in a territory, the more difficult it will be to evict the female. Female flycatchers are known to have the capacity to identify the songs of their own mates and check if they establish a second territory. The primary male was also shown to spend less time in the second territories during incubation periods than before they acquired a secondary mate, especially with greater distances between the two territories.[25][26]

F. hypoleuca (pied flycatcher) and F. albicollis (collared flycatcher) are speciating from each other, providing evidence for speciation by reinforcement (selection against hybrid).[27] The two species diverged less than two million years ago, which is considered recent on the time scale of evolution.[28] Still, hybrids of the two species already suffer from low fertility [29][30] and metabolic dysfunction.[31] It was also believed that sexual selection causes reinforcement and pied flycatcher evolved different colouration in sympatry versus allopatry to prevent hybridization, though some evidence suggests heterospecific competition instead of reinforcement as the underlying mechanism.[32] Mating choice tests of the species find that females of both species choose conspecific males in sympatry, but heterospecific males in allopatry [33] (see conspecific song preference). The patterns could suggest mimicry, driven by interspecific competition; [34] however, song divergence has been detected that shows a similar pattern to the mating preferences.[35]

Eggs off Ficedula speculigera MHNT

Pied flycatcher chicks

The diet of the European pied flycatcher is composed nearly entirely of insects. One study analyzed the stomach contents of birds during the breeding season and found that ants, bees, wasps and beetles made up the main diet.[6] Ants made up approximately 25% of the diet.[41] Food given to nestlings include spiders, butterflies, moths, flies, mosquitoes, ants, bees, wasps, and beetles. For Lepidoptera and Hymenoptera, larvae appear to be consumed more than adult insects; the opposite is true for other insect orders.[39] There is also variation between the proportions of larvae and adult insects between different habitats. Nestlings were also found to consume more spiders, butterfly, and moth larvae, while adult flycatchers consume more ants.[6]

Female in a nestbox in Finland

• mid-September to mid-April: lives in sub Saharan Africa
• mid April to end of May: migrates and arrives in countries such as the United Kingdom
• June to August: breeding season, one brood only
• August to mid September: flies back to sub Saharan Africa

They breed in upland broadleaf woodland. This means that in Britain they are limited due to geography to the North and West. They prefer mature oak woodland, but also breed in mature upland ash and birch woods.

They require very high horizontal visibility - a low abundance of shrub and understorey, but with high proportion of moss and grass. Grazing needs to be managed to maintain this open character, but also allow the occasional replacement trees.

They will sometimes use mature open conifer woodland where natural tree holes occur. Generally they prefer trees that have tree holes, i.e. dead trees, or dead limbs on healthy trees. They also like lichens that grow on trees.

The Forestry Commission offers grants under a scheme called England's Woodland Improvement Grant (EWIG); as does Natural England's Environmental Stewardship Scheme.