Brambling Research Articles

Numerical and functional responses of breeding passerine species to mass occurrence of geometrid caterpillars in a subalpine birch forest: a 30‐year study

In northern Fennoscandia, the geometrid moths Epirrita autumnata and Operophtera brumata have cyclicities in density with mass occurrence at 10‐year intervals. The larvae of Epirrita and Operophtera attain a size of 2–3 cm and 1.5–2 cm, respectively, and are nutritious food items for passerine birds. To examine whether these larvae have any numerical and/or functional influence on a passerine bird community (mountain birch forest in Budal, central Norway) during a 30‐year period (1972–2001), I estimated their abundance (number of larvae per 100 sweeps) in the birch canopy, and the densities of breeding birds in the passerine community. In addition, from 1972 to 1998, I monitored the nesting success of five of the bird species. The foraging pattern of the most abundant bird species and their gizzard contents (adults and nestlings) were examined in 1972–78 (covering population peaks of both the geometrids). Population peaks of Epirrita occurred in 1975–76, 1985–86 and 1996, and of Operophtera in 1976–77, 1986–87 and 1997–98. The passerine community consisted of eight species that were territorial in all 30 years, one species in 26 years, three species in 14–21 years and three species in 1–4 years. Only the Brambling Fringilla montifringilla population responded numerically to the fluctuations of Epirrita and Operophtera. Brambling was also the only species whose mean clutch size varied between years, and this correlated positively with the density of Epirrita. The mean annual nesting success of Willow Warbler Phylloscopus trochilus, Bluethroat Luscinia svecica and Common Redpoll Carduelis flammea tended to be higher in years with mass outbreaks of Epirrita, but was significantly so only for Reed Bunting Emberiza schoeniclus. The abundance of Operophtera larvae showed no influence on the nesting success of any bird species. The passerines foraged more frequently in the birch canopy in the Epirrita outbreak years (1975–76) than in the years before or after. Gizzard analyses of five adult passerine species and their nestlings showed that Epirrita was the main food item in 1974–76. Even though Operophtera occurred in large numbers in birch trees in 1976 and 1977, only a few larvae were found in the gizzards of the passerines. None of the passerines showed an increase in their population density in the year following the larval outbreaks, but the densities of Willow Warbler and Bluethroat increased in the succeeding year, indicating a higher return rate for these species. The study shows the existence of a dietary response and also indicates a reproductive response to the changes in the abundance of Epirrita in mountain birch forest. The lack of numerical response in the passerines (except the Brambling) to the fluctuation in Epirrita contrasts with the pattern described for passerine communities in northern temperate deciduous forests in North America, where Lepidoptera caterpillars periodically have mass outbreaks.

The 37-year dynamics of a subalpine passerine bird community, with special emphasis on the influence of environmental temperature and Epirrita autumnata cycles

The breeding passerine bird community of 9 km2 of a primeval subalpine birch forest in Swedish Lapland was censused yearly from 1963 through 1999. The community density remained stable, fluctuating around a mean value of 403 ± 85 territories/km2. Species richness increased by an average of one species every four years. Twenty species made up 98% of the community and Phylloscopus trochilus (40%) and Fringilla montifringilla (19%) remained the dominant species. The species turnover rate between successive seasons was on average 30%. The mean temperatures in June and July were positively correlated to the community density two years and one year later, respectively, less so for the densities of the individual species. Fringilla montifringilla increased in density during the first two years of each Epirrita autumnata caterpillar outbreak, whereas the other species responded only weakly or not at all. All species tended to fluctuate in parallel (no significant opposite trends) which together with the other results suggests that the investigated bird community is far from saturated.

How is host egg mimicry maintained in the cuckoo (Cuculus canorus)?

To investigate the evolutionary mechanism (host specificity vs. random searching) maintaining mimicry between cuckoo egg appearance and that of different European cuckoo Cuculus canorus hosts, we studied the level of mimicry between the appearance of C. canorus eggs and that of their hosts’ eggs in different habitats in southern Finland by using ultraviolet-visible reflectance spectrophotometry. In the main habitat used by C. canorus for reproduction, eggs laid in nests of different host species differed in appearance. Host use by C. canorus was not related to the abundance of hosts, and the level of mimicry was not related to host abundance in the habitat. Furthermore, a close match between C. canorus egg appearance and that of host eggs within habitats was detected after removing the potentially confounding effect of host abundance. In the only two suitable host species nesting in trees (namely chaffinch Fringilla coelebs and brambling Fringilla montifringilla) we detected changes in C. canorus egg appearance that paralleled those of the two host species. Thus our findings suggest the existence of a correlation between the appearance of C. canorus eggs and that of their hosts’ eggs within different habitat types, and suggest that mimicry is maintained by strict host preferences by each C. canorus female when laying. © 2004 The Linnean Society of London, Biological Journal of the Linnean Society, 2004, 82, 57–68.

Age and sex composition, biometrics, site fidelity and origin of Brambling Fringilla montifringilla wintering in Norfolk, England

We analysed data collected from approximately 2,600 Brambling Fringilla montifringilla caught while attracted to artificial food at a site in Norfolk, England over seven winters. The age and sex composition of trapped birds varied between winters in relation to the total number of birds caught, but no systematic pattern was apparent. During invasion years, when a higher number of birds were present on the study site, the proportion of males was higher. In any one winter, 38–70% of the Brambling were male and 63–86% were juvenile. Very few adult females visited the study site. Males had longer wings than females, by an average of 5–6 mm and the wings of adults averaged 1–2 mm longer than juveniles. There was sexual dimorphism in body weight, with males being on average 2 g heavier than females. Adults were on average 1 g heavier than juveniles. Within winters, mean body weights were higher in warmer months. Between winters, there was significant variation in wing length and body weight, which may have been associated with variation in the geographical origin of the birds or food availability. Approximately 70% of juveniles had undergone a partial moult of the greater coverts, with an average of between 2.7 and 3.4 old greater coverts being retained. Annual variation in the progression of moult was probably due to food availability and weather conditions on the breeding grounds or where the juveniles moulted. The mean proportion of Brambling retrapped within‐winters was 5.7% (range 0–15%) and there was no evidence to suggest that site fidelity was different in invasion years. Recoveries of ringed birds suggest that Brambling over‐wintering in Norfolk originate from Scandinavia and pass through the Low Countries on migration.

Abundance of owls and Bramblings Fringilla montifringilla in relation to mast seeding in south-eastern Sweden

We investigated the relationship between mast seeding in beech Fagus sylvaticus and oak Quercus spp., and the occurrence of the rodent-dependent predators Tengmalm’s Owl Aegolius funereus, Long-eared Owl Asio otus and Tawny Owl Strix aluco in south-eastern Sweden (Blekinge) 1992—2000. We also compared available data on seed production with data on winter flocks of Brambling Fringilla montifringilla, mainly depending on beech seeds as winter food. Years of good beech mast production were followed by years of high frequency of Tengmalm’s Owl and Long-eared Owl, indicating a rapid numerical response to improved food conditions. The Tawny Owl did not respond in the same way, but tended to reach high densities two years after mast seeding. These results suggest that mast seed production may influence the populations of rodent-feeding predators, and that the numerical response may be very rapid in potentially nomadic specialist predators. This was indicated particularly for the Tengmalm´s Owls arriving in Blekinge rather late in spring of 1999. Winters following good beech mast production normally held large numbers of Bramblings. However Bramblings were absent in Blekinge during the winter of 1992/93 despite the very good year for beechnut production in 1992. Thus, low number of Bramblings was no reliable indication for low numbers of owls the following spring.

CIRCADIAN CONTROL OF MIGRATORY RESTLESSNESS AND THE EFFECTS OF EXOGENOUS MELATONIN IN THE BRAMBLING, FRINGILLA MONTIFRINGILLA

Circadian pacemakers control both “daytime” activity and nocturnal restlessness of migratory birds, and the daily rhythm of melatonin release from the pineal has been suggested to be involved in the control of migratory activity. To study the phase relations between the two activity components during entrainment and when free running, locomotor activity of bramblings (Fringilla montifringilla) was recorded continuously under a 12:12 “cool light” to “warm light” cycle (CL:WL, ca. 5000 K and ca. 2500 K, respectively) or blue light to red light cycle (BL:RL, maxima at 440 and 650 nm, respectively) at different irradiance ratios. Migratory activity was expressed primarily during the WL or RL phase of the light cycles. Under free-running conditions, the circadian periods τ correlated with the phase relations between day and night (migratory) activity components during preceding entrainment. Bramblings with migratory activity had significantly longer τ at constant light intensity than the same individuals without migratory activity. Birds with migratory activity reentrained faster after a 6h phase shift of the CL:WL cycle than birds without migratory activity. When exogenous melatonin was given in the drinking water (200 μg/mL 1% ethanol or 0.86 mM) to bramblings exposed to 12:12 CL:WL cycles with constant irradiance, the amounts of activity, which were initially higher during the WL phase of the light cycle, were suppressed to similar low levels during both light phases. The systematic changes in the amounts of activity during melatonin treatment were not correlated with consistent changes in entrainment status. The data support the hypothesis that changes in the amplitude and level of the daily melatonin cycle are involved in regulating migratory restlessness, by either allowing or inhibiting nocturnal activity. (Chronobiology International, 17(4), 471–488, 2000)

Spectral Composition of Light as a Zeitgeber for Birds Living in the High Arctic Summer

The hypothesis was tested whether periodic changes in spectral composition of light are an effective zeitgeber for synchronization (entrainment) of circadian rhythms of birds breeding in the high arctic summer. Two palearctic passerine birds, the brambling ( Fringilla montifringilla) and the common redpoll ( Carduelis f. flammea), which both breed during summer at latitudes above the Arctic Circle and migrate to temperate zone latitudes for wintering, were studied. To investigate the effect of daily alterations in light spectrum, bramblings were tested under 24-h cycles of fluorescent lights of different color temperatures (12 h at ca 5,000 K and 12 h at ca 2,500 K) and energy ratios varying between 16:1 and 0.3:1. Entrainment of activity rhythms occurred at energy ratios of 1:1 (in all seven birds tested) and 0.8:1 (in three of seven birds tested) with activity mostly within the “blue” phase (ca 5,000 K). Light cycles alternating between narrow spectral ranges of blue (max. at 440 nm) and red (max. at 650 nm) and energy ratios of 1:1 and 1.1:1 (equivalent to ratios of photons flux of ca 0.67:1 and 0.73:1, respectively) were also effective in entraining the bramblings' activity rhythms (8 and 9 of 11 birds, respectively) with activity occurring primarily during the red phase. The activity rhythms of most common redpolls tested also entrained to blue:red light cycles (B:R 16.5:7.5 h) with equal energies during the blue and red phase (equivalent to a photons flux ratio of ca 0.67:1). The results support the hypothesis that passerine birds breeding in the arctic during summer may use the daily changes in spectal composition of sunlight as a zeitgeber for synchronizing physiological and behavioral rhythms, if changes in light intensity are not a reliable environmental cue.

Egg sizes of nine passerine bird species in a subalpine birch forest, Swedish Lapland

Egg measurements together with calculated volumes are presented for nine passerine species (Prunella modularis, Luscinia svecica, Phoenicurus phoenicurus, Turdus pilaris, Turdus philomelos, Turdus iliacus, Phylloscopus trochilus, Fringilla montifringilla, and Carduelis flammea), breeding in rich subalpine birch forests on a south-faced mountain slope in southern Swedish Lapland. There were no clear regional size trends in comparisons with egg collections from other parts of Europe. There was a significant increase in egg size in the latter part of the laying sequence. The ultimate egg is from 2.1% (F. montifringilla) to 6.5% (Ph. trochilus) larger than the mean of the clutch. According to several years’ measurements of T. pilaris and T. iliacus eggs there was no significant size variation between seasons. This constancy together with the relatively large egg sizes might be a consequence of the productive breeding habitat of the study area.

Male aggressiveness and the possible occurrence of group territoriality in the Brambling Fringilla montifringilla

Bramblings are nomadic birds with an interesting breeding ecology. Their nests are often aggregated in groups of two to eight nests. Such aggregated nesting may indicate the existence of group territories, probably formed for anti-predatory purposes. The male Bramblings show much variation in colour pattern during the breeding season, with individuals ranging from completely black-hooded to virtually female-like grey-hooded. The colour pattern is probably age dependent, but may also be correlated with social status. The present study of breeding Bramblings was performed during the summer 1998 at Ammarnäs, County of Västerbotten, Sweden. We simulated an intrusion in the breeding territory, using an artificial intruder (a decoy) and a tape recorder with Brambling song, to find evidence for the group territory hypothesis and to investigate the possible correlation between male plumage pattern and aggressiveness. Only intermediate males (type 2) and black-hooded males (type 1) (i.e. no female-like males), were observed during experiments at 13 nests. The type 2 males were slightly more active and aggressive towards the intruder-decoy (an intermediate male), when tested close to the nest, than were the type 1 males. The decoy was never attacked by more than one male at a time, but there were more than one male present in 77% of the experiments, which does not exclude the possibility for the existence of a group territory.

Rapid decline of host defences in response to reduced cuckoo parasitism: behavioural flexibility of reed warblers in a changing world

On Wicken Fen and nearby watercourses eastern England, parasitism by cuckoos, Cuculus canorus, declined from 26 and 16 of reed warbler (Acrocephalus scirpaceus) nests in 1985 and 1986, respectively...

First Breeding Records of Whooper Swan and Brambling in North America at Attu Island, Alaska

We document the first breeding records of Whooper Swan (Cygnus cygnus) and Brambling (Fringilla montifringilla) in Alaska and North America on Attu Island in the Western Aleutians in the spring of 1996. Five cygnets were seen with adults and the nest located, and a territorial pair of Bramblings was observed and a nest with eggs found.

A Brambling at Claresholm, Alberta During Winter 1993–1994

A Brambling at Claresholm, Alberta During Winter 1993–1994

Daily rhythm of oxygen consumption and thermoregulatory responses in some European winter- or summer-acclimatized finches at different ambient temperatures

The oxygen consumption of European finches, the siskin (Carduelis spinus), the brambling (Fringilla montifringilla), the bullfinch (Pyrhulla pyrhulla), the greenfinch (Carduelis chloris) and the hawfinch (Coccothraustes coccothraustes), was recorded continuously while ambient temperature was decreased stepwise from +30 down to-75°C. The oxygen consumption, body temperature (telemetrically), and shivering (integrated pectoral electromyography) of greenfinches were measured simultaneously at ambient temperatures between +30 and-75°C. Maximum heat production, cold limit, lower critical temperature, basal metabolic rate and thermal conductance (of the greenfinch) were determined. The diurnal variation of oxygen consumption of siskins and greenfinches was recorded at thermoneutrality and below the thermoneutral zone in winter- and summer-acclimatized birds. The diurnal variation of body temperature and thermal conductance of greenfinches were also determined. The diurnal variation of heat production was not seasonal or temperature dependent in the siskin and in the greenfinch. Nocturnal reduction of oxygen consumption saved 15–33% energy in the siskin and greenfinch. Body temperature of the greenfinch was lowered by 2.5–3.4°C. The nocturnal reduction of thermal conductance in the greenfinch was 39–48%. The basal metabolic rate was lowest in the largest bird (hawfinch) and highest in the smallest bird (siskin). The values were in the expected range. The heat production capacity of finches in winter was 4.7 times basal metabolic rate in the siskin, 4.2 times in the brambling, 3.5 times in the greenfinch and 2.9 times in the bullfinch and hawfinch. The heat production capacity of the siskin and greenfinch was not significantly lower in summer. The cold limit temperatures (°C) in winter were-61.2 in the siskin,-41.3 in the greenfinch,-37.0 in the bullfinch,-35.7 in the brambling and-28.9 in the hawfinch. The cold limit was 14.3°C higher in summer than in winter in the siskin and 8.7°C in the greenfinch. Thermal insulation of the greenfinch was significantly better in winter than in summer. The shivering of the greenfinch increased linearly when ambient temperature was decreased down to-40°C. Maintenance of shivering was coincident with season. In severe cold integrated pectoral electromyography did not correlate with oxygen consumption as expected. The possible existence of non-shivering thermogenesis in birds is discussed. It is concluded that the acclimatization of European finches is primarily metabolic and only secondly affected by insulation.

Flycatching behaviour in some passerines during the late breeding season at Ammarnäs, Swedish Lapland

Many passerines have been recorded flycatching in the late breeding season in northern Swedish forests. In this paper, I analyze how flight energy costs according to Minimum Energy Power (sensu Pennycuick 1989) correlated with flycatching behaviour. Species included are (with increasing rank of flight energy cost): Spotted Flycatcher Muscicapa striata, Whinchat Saxicola rubetra, Yellow Wagtail Motacilla flava, Reed Bunting Emberiza schoeniclus, Brambling Fringilla montifringilla, and White Wagtail Motacilla alba. On average, birds performed 0.6–2.3 flights/30s and captured from 0 up to 10 prey per flight. Number of prey captured per flight varied significantly among species (from 0.8 to 1.1 prey). The efficiency of capturing prey (percentage of successful single capture flights) also varied between species, from 72% in the Whinchat to 97% in the White Wagtail. The percentage of multi-capture flights did not, however, vary. In two species, the multi-capture flights significantly reduced the time spent flying per prey. Flight energy costs were positively correlated with flycatching rate and number of prey captured per flight. The extensive use of flycatching is interpreted as an opportunistic response to local super-abundance of highly rewarding prey, mostly insects Isoperla grammatica, O. Plecoptera, during a period of presumed high energetic demands by birds.

Structure of a Brambling Fringilla montifringilla roost according to sex, age and body‐mass

In a winter roost of several hundreds of thousands of Bramblings Fringilla montifringilla, the composition of birds roosting at the periphery and of birds flying into the centre of the roost was studied regarding sex, age, size and body‐mass. At the periphery of the roost, more females were present than in the centre, and their proportion increased with decreasing density at the periphery. No significant difference in age classes was found between centre and periphery, but adults flew into the roost later than first year birds. Within sex‐age classes, birds in the centre were heavier but not larger than birds at the periphery. The difference in body‐mass between centre and periphery was more pronounced in small than in large birds within each sex‐age class.Because strong competition for particular positions within the roost was observed, it is inferred that the quality of roosting positions varied and that females and/or light birds were displaced toward the periphery. Predation and microclimate are discussed as possible reasons for the variation in the quality of roosting positions and for the lower energy reserves of birds roosting at the periphery.

The primary moult of the Brambling Fringilla montifringilla evaluated by four different methods

The primary moult of the Brambling Fringilla montifringilla was studied between 1988 and 1991 at Ånnsjön (63°15'N; 12°28'E) in the Swedish mountain region. The duration of primary moult was estimated in four different ways: 1) By linear regression of population data; 2) By calculating the mean duration of moult of 34 recaptured birds, assuming a linear relationship between time and moult progression; 3) By using data from the same recaptured birds but correcting for the non-linear progression of moult; 4) By using field data on the rate of shedding of different primaries and the growth rate of individual feathers to construct a moult score versus time curve. Linear regression of population data gave results varying from 32 to 70 days depending on population and method of analysis. The other three methods all resulted in a primary moult duration of 58–60 days. The recaptured birds often showed a weight decrease between captures but this seemed not to affect the moult speed. The mean starting date of moult of the population varied from 8 July to 18 July in the four years. The males tended to start a little earlier than the females, but the difference is not significant. The estimated duration of primary moult (ca 59 days) is considerably longer than the result (46.5 days) of another recently published study. The difference is probably due to different methods of analysis.

Brambling: A Eurasian Visitor to Saskatchewan

Brambling: A Eurasian Visitor to Saskatchewan

Adaptations of bramblings and chaffinches towards parasitism by the common cuckoo

A coevolutionary arms-race between the common cuckoo, Cuculus canorus, and its hosts includes adaptations such as mimetic cuckoo eggs and counter-adaptations such as rejection of the parasitic eggs and aggression towards the parasite by the host. To investigate the existence of defence mechanisms in two species not so far reported as being cuckoo hosts in Norway, but considered to be suitable as hosts, experiments were carried out on bramblings, Fringilla montifringilla, and chaffinches, F. coelebs. Since there were no statistically significant differences between the two species in the way they treated foreign eggs, the data were pooled. The birds rejected about 80% of both non-mimetic and mimetic, artificial, cuckoo eggs, and many even ejected some conspecific eggs. Reports of cuckoo eggs mimicking brambling eggs, in Finland early in the present century, suggest a rapid spread of rejecter alleles. Although never observed in either bramblings or chaffinches, intraspecific nest parasitism is proposed as a possible factor to account for the rejection of conspecific eggs. The parent bramblings attacked a stuffed dummy cuckoo aggressively, but the presence of a stuffed cuckoo led to no increase in the rejection rate of conspecific eggs.

Primary moult of the Brambling Fringilla montifringilla in northern Sweden

The postnuptial wing moult of the Brambling was studied in a subalpine birch forest near Ammarnäs (65°58'N, 16°07'E) in Swedish Lapland. 580 moult cards were collected during an annual ringing scheme in the years 1984—1989. Regression analysis of moult data, with date as the independent value, showed an average moult duration for males and females of 47 days. Raggedness values support the moult speed estimated from the regression analysis. The moult speed shown here for the Brambling is much faster than for the Chaffinch and might be due to some constraint for moulting during early autumn.

Population trends of forest birds in a Finnish Lapland landscape of large habitat blocks: Consequences of stochastic environmental variation or regional habitat alteration?

Birds were counted in Northern Finnish Lapland in an area situated 200 km north of the Arctic Circle in virgin forests in the 1940–1950s, and both in virgin and managed forests in 1982–1989. The area consisted of very large habitat patches: blocks of virgin and managed forests were separated and covered hundreds of square kilometers. The most abundant species fluctuated similarly both in virgin and managed forests in the 1980s. The yearly total density of tropical migrants (insectivores) was negatively correlated with the number of cold days in spring. Short-distance migrants were probably more affected by weather conditions during migration and wintering area. Species which increased and those which decreased in Northern Finland due to habitat alteration had no such trends in large virgin forests, either from the 1940–1950s to the 1980s or during the 1980s. The brambling Fringilla montifringilla was the only species having a significant within-habitat trend: it increased from 1940 to the 1950s but decreased in the 1980s. The brambling is a forest-habitat generalist, and therefore its trends are not likely to be explained by habitat alterations caused by forestry. Year-to-year variations in densities of species seem to reflect stochastic environmental changes, such as in weather conditions and seed crop. Regional population changes caused by habitat alteration are not reflected in population densities in large virgin forests. The northern taiga species preferring virgin forests ( Tetrao urogallus, Picoides tridactylus, Parus cinctus, Perisoreus infaustus and Pinicola enucleator) have drastically declined in the whole of Northern Finland due to habitat loss caused by forest management. These decreased species seem to survive in large, virgin forest, and therefore the protection of these old-aged coniferous forests is essential.