The utilization of heather moorland by territorial Red Grouse Lagopus lagopus scoticus

Although the breeding density of Red Grouse Lagopus lagopus scoticus is related to the density of burned patches of heather Calluna vulgaris , territories appear to offer surplus food, and other factors, especially the risk of predation, may be important. In order to determine how Red Grouse make use of heather moorland, an individually marked population was studied on a moor in northeast Scotland from 1992 to 1994. Territorial birds preferred stands of tall heather during the daytime in autumn and winter, but in spring they increased their use of heterogeneous heather/grass mixtures. Furthermore, in spring, females showed a very strong affinity for edges between heather stands of different ages, where they had easy access to nutritious young heather and good cover. When near the vegetation edge, territorial birds spent most time on the side of the edge providing greater cover. Broods occupied ranges in areas with rather more old heather and with more edge than was available over the entire study site. Within their ranges though, broods clearly preferred heterogeneous areas during the first month after hatching, and showed a further preference for vegetation edge. Their behaviour changed during the second month after hatching, when they utilized tall heather to a greater extent, but edge remained important.     

A long-term large-scale study of the breeding biology of the Spanish imperial eagle (Aquila adalberti)

We present data from a 17-year study of the population biology of a growing population of Spanish imperial eagles Aquila adalberti across most of its breeding range. The objective of this study was to analyse the effects of age, supplemental feeding and rabbit haemorrhagic disease (RHD) on several breeding parameters of this population of eagles. Average clutch size was 2.2 eggs per clutch, and the average incubation time was 41.7 days per clutch. Fledging occurred an average of 76.8 days after hatching, the length of the fledgling period was not correlated to clutch size. The annual average percentage of pairs laying eggs was 88%. A significant reduction in the percentage of pairs laying eggs in the period 1992–1994 (from 91 to 81%) coincided with most of the eagles’ territories being affected by the rabbit epizootic disease, RHD, which reduced their food supply significantly. Average productivity was 1.23 chicks per monitored territory, average breeding success was 1.40 chicks in a clutch per territory and the average fledging rate was 1.69 chicks per territory with hatching success. The main known causes of breeding failure during incubation were nest collapse and human disturbance. During chick-rearing, total or partial chick losses were mainly caused by siblicide, disease, malnutrition or nest collapse. In 26.2% of the 1372 monitored breeding attempts, at least one of the breeding birds was a subadult (the male in 56.1% of the cases, the female in 15.5% and both sexes in 28.4% of cases). In cases of mixed-aged pairs (n = 205), 70.7% were the result of a substitution, and 29.3% were the result of the forming of a new pair. Egg laying took place significantly earlier and breeding success was higher in territories occupied by adults than in those occupied by subadults. Breeding parameters were higher in high-quality (rabbit-rich) territories than in low-quality (rabbit-poor) territories, but only for those territories occupied by adults. The values obtained in the territories occupied by adults were only significantly higher than in those of the subadults in high-quality territories. Age and territory quality thus simultaneously affected reproductive output.     

Territory quality, survival and reproductive success in southern emu-wrens Stipiturus malachurus

Multi-factor analyses of territory quality in relation to fitness components of adults are rare, especially in non-migratory species. I studied the influence of multiple attributes of territory quality (habitat type and the abundance of food and predators) on the reproductive success and survival of a threatened Australian passerine, the southern emu-wren Stipiturus malachurus . The abundance of frequently-selected prey types (lepidoptera, diptera, hemiptera and larvae) varied significantly across territories according to habitat type. Reproductive success (number of offspring fledged) was highest in territories containing a greater proportion of tall shrubland, which had the highest insect abundance of any habitat. Closed heathland and sedge/rushland also had high food abundance compared to other habitat types, but higher fledging success occurred only within closed heathland, possibly because predator density was lower in this habitat type. High snake density was associated with reduced adult survival during the breeding season and a lower probability of nest success. In sedge/rushland, any benefits of prey abundance may therefore be offset by a high density of predators. Emu-wren age and size were unrelated to breeding output of pairs, suggesting that ecological factors may swamp effects of individual quality on emu-wren fitness components. Preservation of tall shrubland and closed heathland habitats appear to be of key conservation priority for emu-wrens.     

Seasonal reproductive success of the Moorhen Gallinula chloropus: the importance of male weight

During a three-year study of 82 pairs of Moorhens Gallinula chloropus, seasonal reproductive success (SRS) varied greatly between pairs. Pairs on big territories had a higher SRS than pairs on small territories, probably because clutch survival was higher on big territories. Pairs that began breeding early had a higher SRS than pairs that began late because early breeders laid larger clutches and could attempt more broods. Pairs with heavy males had bigger territories and began breeding earlier than pairs with light males. Heavy males therefore had a higher SRS than light males. Female weight did not affect territory size, timing of breeding, or female SRS. Assuming SRS to be a good predictor of lifetime reproductive success, selection should favour heavy males but not heavy females. Male Moorhens are significantly heavier than female Moorhens. Finally, pairs with breeding experience had a higher SRS than pairs without, because they had bigger territories and began breeding earlier. However, males in inexperienced pairs were not lighter than males in experienced pairs, so it is not clear why they defended smaller territories or laid later.     

Winter territoriality and its implications for the breeding ecology of White-throated Dippers Cinclus cinclus

Capsule: Pairs of White-throated Dippers Cinclus cinclus which defended winter territories bred earlier than non-territorial individuals, but there was no difference in reproductive success.

Aims: The effect of winter territoriality on breeding ecology has rarely been studied in resident birds. We carried out a preliminary investigation of whether winter territorial behaviour and territory size affect the timing of reproduction, breeding territory size and reproductive success in a riverine bird, the White-throated Dipper.

Methods: We monitored an individually marked population of White-throated Dippers in the UK. Wintering individuals were classified as either territorial or ‘floaters’ according to their patterns of occurrence and behaviour, and their nesting attempts were closely monitored in the subsequent months. Winter and breeding territory sizes were measured by gently ‘pushing’ birds along the river and recording the point at which they turned back.

Results: All birds defending winter territories did so in pairs, but some individuals changed partners before breeding. Territorial pairs that were together throughout the study laid eggs significantly earlier than pairs containing floaters and those comprising territorial birds that changed partners. However, there were no significant differences in clutch size, nestling mass or the number of chicks fledged. There was no relationship between winter territory length and lay date or any measure of reproductive success, although sample sizes were small. Winter territories were found to be significantly shorter than breeding territories.

Conclusion: Winter territoriality may be advantageous because breeding earlier increases the likelihood that pairs will raise a second brood, but further study is needed. Territories are shorter in winter as altitudinal migrants from upland streams increase population density on rivers, but this may also reflect seasonal changes in nutritional and energetic demands.     

Foods of the Dartford warbler Sylvia undata on southern English heathland (Aves: Sylviidae)

This paper describes the invertebrates of Callunetum and gorse on lowland heaths in Dorset and relates how these were exploited by the Dartford warbler Sylvia undata , a scarce bird of interest to nature conservation and one of the small number of wholly insectivorous resident passerines in Britain. Gorse had a denser invertebrate fauna than Callunetum and was used for feeding at a frequency out of proportion to its abundance. Diets of adult birds closely reflected the taxonomic composition of the gorse and Callunetum faunas exploited in the observed proportions, though some noxious taxa were avoided and below a certain limit, creatures of above average size were selected. Major foods were beetles, spiders, lepidopteran larvae and bugs. Nestling birds received a diet differing in taxonomic composition and size from that of the adults, and variations between habitats were found which accorded with observations on the habitat preferences of the Dartford warbler. An experimental investigation showed the importance of gorse as a source of food for young and the adults flew considerable distances ignoring extensive deep stands of heather nearer to the nest. The possible influence of competing insectivorous vertebrates on Dartford warblers is discussed. Various mammals and reptiles appeared to be the major vertebrate predators in Callunetum, but little competition was anticipated in gorse. Scarcity of gorse on the heaths and low densities of invertebrates in heather explained the low densities at which Dartford warblers occur.     

The habitat use and diet of Black Grouse Tetrao tetrix in the Pennine hills of northern England

The habitat and dietary preferences of Black Grouse were studied from 1989 to 1991 in a largely treeless habitat within a 17 km² area of the Pennine hills of northern England using radiotelemetry. Grassland habitats were preferred by 84% of 19 birds for much of the year and heather moorland was selected in winter; the other birds, all females, remained in heather habitats all year. Most females reared broods in damp, rushy grass moorlands, but one of six broods used hay fields. Diet closely reflected seasonal plant availability in selected habitats and the leaves, flowers, fruits and seeds of a wide variety of plants were eaten. Cotton-grass Eriophorum vaginatum was important in spring, grassland herbs, grasses, sedges and rushes in summer and autumn and Ling Heather Calluna vulgaris in late autumn and winter. Males fed substantially more on heather in winter than females which partially replaced heather in their diet with the leaves of grasses and herbs. Young chicks showed considerable preference for Sawfly (Symphyta) larvae. Suggested management recommendations include the regulation of sheep-grazing, encouragement of wet flush areas and the late cutting of hay fields.     

Daughters on request: about helpers and egg sexes in the Seychelles warbler

The Seychelles warbler (Acrocephalus sechellensis) was an endangered endemic of the Seychelles islands where, until 1988, the entire population of ca. 320 birds was restricted to the one island of Cousin Island (29 ha). Additional breeding populations were successfully established on the islands of Aride (68 ha, 1988) and Cousine (26 ha, 1990) and now with the existence of ca. 2000 warblers on three islands the conservation status of the warbler has improved from endangered to vulnerable. Emigration from the island is extremely rare, so birds that disappeared were known to have died. Almost every bird on Cousin Island has been individually colour ringed and monitored throughout all breeding attempts during a 17-year period (1985-2002; total ca. 2400 birds). These birds were also blood sampled for molecular parentage and sex analyses. Therefore the lifetime reproductive success of many birds is known. Although warblers can breed independently in their first year, some individuals remain in their natal territory as subordinates, and often help by providing nourishment to non-descendant offspring. The frequency of 'helping' is affected by habitat saturation and variation in territory quality (insect prey availability). The long-term benefits of helping are higher for daughters than for sons, and it is therefore no wonder that most helpers are daughters from previous broods. Furthermore, on low-quality territories breeding pairs raising sons gain higher fitness benefits than by raising daughters, and vice versa on high-quality territories. Female breeders adaptively modify the sex of their single-egg clutches according to territory quality: male eggs on low quality and female eggs on high quality. The Seychelles warbler is a beautiful example of behavioural and life-history adaptations to restricted circumstances.     

Territorial breakdown of black-capped chickadees, Poecile atricapillus, in disturbed habitats?

The propensity of males to behave territorially may be greatly affected by the perceived quality of the habitat. In suboptimal habitats, the cost of defence may be prohibitively large compared to the associated benefits, and territorial behaviour may be expected to decline. We tested this hypothesis in a population of black-capped chickadees breeding in adjacent habitats: one habitat consisted of an 85-ha patch of early seral forests regenerating after clear-cut logging (disturbed site), and the other consisted of an 85-ha patch of mature mixed-wood forests (undisturbed site). Breeding success of pairs in the disturbed site was significantly lower than in the undisturbed site, suggesting a difference in the relative quality of the two habitats. During the spring of 2000 and 2001, we mapped the actively defended areas and song posts of colour-marked chickadees and found that pairs occupying the disturbed site were subject to more territorial intrusions than pairs in the undisturbed mature woodlands. Five pairs of chickadees in the disturbed habitat and five pairs in the undisturbed habitat were radiotagged and we conducted repeated focal observations on the movement patterns of the birds. All five pairs in the disturbed habitat regularly intruded into areas actively defended by neighbouring birds; only one of the five pairs in the undisturbed habitat ever intruded onto the known territory of another pair during an observation period. Our results suggest that the quality of the disturbed habitat may have been sufficiently low so as to make normal levels of exclusive defence cost inefficient. Conversely, birds in disturbed habitat may have intruded more frequently into neighbouring territories because resource levels in their own exclusively defended territory were insufficient to meet energetic requirements during the breeding season.     

Reproductive success and survivorship of the Galapagos Hawk Buteo galapagoensis: potential costs and benefits of cooperative polyandry

The Galapagos Hawk Buteo galapagoensis is one of few species showing cooperative polyandry. As many as four males may mate with one female and share a territory and nest, Such groups, on average, produce more young than monogamous pairs, but on a per male basis (assuming that each male of a group has an equal chance to fertilize each young) polyandrous males produce fewer young per year than monogamous males. Territorial breeding birds show higher yearly survivorship (90%) than non-territorial, non-breeding birds (50% or less). All territorial birds seem to remain on their territories for life, and monogamous pairs actually constitute the remnants of polyandrous groups. Some potential factors producing such an unusual system are discussed. Limited breeding space and high mortality among non-territorial birds seem to work in favour of group breeding in this and other cooperative species. Polyandry may be favoured because of the reduced value of extra females in hawk breeding behaviour. Equal-status males may occur because of the lack of kinship among cooperating males and the high potential genetic cost of being a helper in a long-lived, low fecundity species. Other possible factors favouring group breeding are territory acquisition and the variable nature of the Galapagos climate.     

Territory acquisition during winter by juvenile Willow Tits Parus montanus

Willow Tits Parus montanus live within exclusive territories in non-kin winter flocks with a dominance hierarchy in which males dominate females and adults dominate juveniles. Because they live in habitats that are saturated with dominant territory owners, the options of subordinate juveniles surviving the winter are: (1) to become a dominant owner of a vacated territory, (2) to stay in an occupied territory and hope for ownership or (3) to leave the area and hope for territory acquisition elsewhere. Removal experiments during December to February revealed that particularly the most dominant of the juvenile pairs left their own flock territory and replaced birds experimentally removed from a neighbouring flock, if by doing so they increased their own dominance position. It is suggested that juvenile Willow Tits updated their information about the composition and dominance structure of adjacent winter flocks by regularly visiting these territories and attempted to become dominant owners during winter, thereby increasing their chances of breeding.     

Seasonal change in Red-backed Shrike Lanius collurio territory quality - the role of nest predation

This paper examines the relationships between territory preference, reproductive performance and nest predation in a Red-backed Shrike Lanius collurio population breeding in rapidly changing farmland. Territory preference was measured by (a) the order of laying dates in territories within years and (b) territory occupation frequency over a five-year period. Seven environmental variables were tested but only the density of Sloe (Blackthorn) Prunus spinosa in territories was correlated positively with territory occupation frequency. Within years, Red-backed Shrikes started to breed earlier in territories with more Sloe, but reproductive performance was not related consistently to territory differences. A high proportion of Sloe-rich territories was vacant each year. Thus, the observed negative association between settlement order and amount of Sloe may reflect a seasonal change in habitat preference. Early breeders prefer Sloe-rich territories whereas late birds prefer Sloe-poor territories. Supporting evidence is that the proportion of occupied territories that was Sloe-rich was higher for early than for average or late first breeding attempts. Moreover, in contrast to early in the season, the probability of a replacement clutch following nest failure was not associated with the amount of Sloe, but increased with increasing densities of Juniper Juniperus communis. Late in the nesting season, pairs breeding in Sloe-rich territories suffered higher nest predation than those breeding in Sloe-poor territories. In early nesting attempts, however, the relationship was reversed. Nest predation is probably an important selective agent on habitat selection since it was the principal factor explaining variation in the numbers of fledglings produced among territories. Thus, the Red-backed Shrike may shift territorial preferences adaptively as the season progresses to match within-season changes in predation pressure in different types of territories.     

Effect of human activities on Egyptian vulture breeding success

Habitat loss, electrocution on power poles and persecution by humans are the main threats to birds of prey. Nevertheless, the effects of human disturbance on endangered species are becoming notorious due to the increasing recreational use of the natural environment. We evaluated the effects of human disturbances on Egyptian vulture Neophron percnopterus breeding success and developed conservation measures based on minimum distance of effect and buffer areas in a high human density area of northern Spain. A total of 100 breeding attempts of 15 breeding pairs were monitored over 8 years. Human disturbances affected 42 of the breeding attempts. Those disturbances related to and originating in forestry work had the most severe effect on breeding success, being associated with the loss of 100% of 13 breeding attempts, while human disturbances related to free-time activities caused 44% failures in 25 breeding attempts by four pairs, two of them within Natural Parks. The breeding success was significantly less in territories affected by disturbances than in those free of disturbances. Some pairs affected by disturbances changed their nest site, increasing breeding success. Adults were prevented from entering the nest to feed chicks when anyone was detected at an average distance of 307 m, while an average distance of 837.5 m allowed them access. The maximum alert distance was estimated at 605 m and the buffer area was 57 ha. We discuss the application of our results for management schemes and conservation of this species.     

Plumage brightness predicts non-breeding season territory quality in a long-distance migratory songbird, the American redstart Setophaga ruticilla

Many species of birds exhibit brilliant ornamental plumage, yet most research on the function and evolution of plumage has been confined to the breeding season. In the American redstart Setophaga ruticilla , a long-distance Neotropical-Nearctic migratory bird, the acquisition of a winter territory in high-quality habitat advances spring departure and subsequent arrival on breeding areas, and increases reproductive success and annual survival. Here, we show that males holding winter territories in high-quality, black mangrove habitats in Jamaica have brighter yellow-orange tail feathers than males occupying territories in poor-quality second-growth scrub habitats. Moreover, males arriving on the breeding grounds from higher-quality winter habitats (inferred by stable-carbon isotopes) also had brighter tail feathers. Because behavioral dominance plays an important role in the acquisition of winter territories, plumage brightness may also be related to fighting ability and the acquisition and maintenance of territories in high-quality habitat. These results highlight the need for further research on the relationships between plumage coloration, behavior, and the ecology of over-wintering migratory birds.     

Aggressiveness in king penguins in relation to reproductive status and territory location

King penguins, Aptenodytes patagonicus, vigorously defend small territories in very dense colonies. The egg-laying season lasts approximately 4 months, but only pairs that reproduce during the first half of the period succeed in fledging a chick. I examined various factors affecting aggressiveness of king penguins during the breeding season and focused on the differences between central and peripheral territories. Pairs on peripheral territories experienced twice as many encounters with avian predators as did central birds. The vast majority of peripheral birds were late breeders, indicating that reproductive success was very low among penguins defending a territory on the edge of the colony. Time invested in territory defence and rate of agonistic encounters between breeding neighbours increased from the incubation to the brooding period. Parents gave most threat displays to territorial neighbours when the chick was very young and just before crèche formation. Distance to colony edge was not related to aggressiveness in incubating birds, however, the rate of pecking and flipper blows increased from the edge to the centre during brooding. In addition, aggressiveness of breeding penguins towards travelling birds trespassing into their territory increased with distance to edge. Early breeders were not more aggressive than late breeders but the proportion of time spent in territory defence increased with the number of days a bird had spent incubating. As expected, I did not detect any sex difference in aggressive behaviour. Birds occupying territories on the beach were generally more aggressive during the incubation period than those located on the valley sides. Reproductive status (incubating versus brooding) and territory location were the main factors explaining the various levels of aggressiveness observed in breeding king penguins. Copyright 2000 The Association for the Study of Animal Behaviour.     

Assessment of territory quality and its effects on breeding success in a migrant passerine, the Wheatear Oenanthe oenanthe

This paper examines how a returning migrant assesses the quality of an area as a breeding territory before the period of peak food demand and how effective the assessment is in terms of breeding success. Male Wheatears Oenanthe oenanthe return from Africa to choose territories in the Breckland of eastern England about March, females arriving shortly after males. The food supply was predictable: prey densities during the breeding period (egg-laying to chick independence) were strongly correlated with prey densities at the same sites during the period of arrival and territory establishment. Prey densities were also related to vegetation structure, averaging highest on short turf. Male arrival date and territory size were not significantly related to prey density but were strongly related to vegetation structure, implying that birds used vegetation as an indirect clue to prey availability. Neither territory size nor nest spacing appeared to affect nest losses caused by predators. The major variations in number of young fledged (other than predation) were caused by the number of nestlings hatched and presence of a second brood. Both early arrival and an early first brood improved first-brood success and were necessary for a second brood. Not all birds which arrived early bred early enough for a second brood. First-brood hatching date was strongly negatively correlated with pre-breeding prey availability but not significantly related to vegetation structure. Thus by using vegetation as a clue to habitat quality, some pairs suffered reduced breeding success. This result implies that birds may not be able adequately to assess prey density directly at the time of territory establishment. The critical period for food availability may not be the period of peak demand (nestling period), when food is relatively abundant, but is probably the pre-breeding period when females must accumulate reserves for eggs and when the food supply is poor. Food supply during this period may determine the timing of breeding and the ability to rear a second brood, and may thus have a greater effect on breeding success.     

Accepting unrelated broods helps replacement male yellow-headed blackbirds attract mates

Replacement male yellow-headed blackbirds (Xanthocephalus xanthocephalus)did not destroy broods sired by the previous territorial maleand they showed no aggression toward females with unrelatedbroods. To test whether their tolerance of unrelated young wasmisdirected normal parental care, we removed males from experimentalterritories after primary nests were completed but before secondarynests were initiated. Replacement males fed young that theypresumably had sired in secondary nests and ignored foster youngin primary nests, whereas control males fed young in their primarynests. To identify potential benefits of accepting unrelatedyoung, we analyzed patterns of within-season breeding dispersaland of female settlement on territories following nest lossesto predators. Although some female yellowheads do renest onthe same territory following nest failures, the number of nestsinitiated on territories after a predation event was significantlylower than the number initiated on territories without predationover the same period of time. This implies that late-settlingfemales use the number of active or failed nests and/or thenumber of females on a territory when choosing where to breed.If replacement males that accepted unrelated offspring attractmore new females in the remainder of the current breeding seasonthan infanticidal males, then tolerance of unrelated young byreplacement males may be adaptive in some polygynous birds.     

Habitat selection and reproductive success of Ortolan Buntings Emberiza hortulana on farmland in central Sweden – the importance of habitat heterogeneity

Many granivorous birds have shown severe population declines in Europe during recent decades. The aim of the present study was to analyse habitat preferences and reproductive success of one such species, the Ortolan Bunting Emberiza hortulana, in different farmland habitats in south‐central Sweden. Four seemingly different land‐use types were preferred: permanent set‐asides, short rotation coppice, and grazed and unmanaged semi‐natural pastures. Territories and random sites differed considerably in the proportion of these preferred land‐use types; 39% of territories had > 70% preferred habitat (at the 100‐m scale) compared to 5% of random sites. In contrast, 22% of territories and 65% of random sites had no preferred habitats. All the preferred habitats had heterogeneous ground vegetation characterized by patches with bare ground, or at least sparse ground vegetation, intermixed with patches with taller vegetation. Ortolan Buntings also preferred a heterogeneous habitat structure with occurrence of field islets, shrubby edges, barns and electric wires, which could act as song posts or suitable nest‐sites, in 88% of territories. At a larger (1‐km square) scale, territories occupied by pairs aggregated strongly in areas with high proportions of preferred habitats. The number of territories with single males correlated positively with the number of pairs, which suggests that conspecific attraction may influence territory distribution. No measured habitat factors were related to reproductive success. However, due to habitat preferences and the higher proportion of paired males in one habitat type (set‐aside), the production of young (fledglings/ha) is expected to be higher in set‐asides, as well as in short‐rotation coppices and semi‐natural pastures. Thus, these habitats are important for the conservation of the Ortolan Bunting. Large areas with habitat structures such as field islets are especially important because the Ortolan Bunting breeds in aggregations in these areas.     

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.     

Complex effects of habitat loss on Golden Eagles Aquila chrysaetos

The development of commercial forests presents potential threats to large raptors that rely on prey caught in open country. We examined the effect of afforestation of breeding habitat used by a population of Golden Eagles Aquila chrysaetos in Scotland where, over the last 50 years, extensive stands of exotic conifers have been planted. Using data for 31 years on territory occupancy and breeding success, together with spatiotemporally dynamic mapping of forest cover and predicted areas of territory‐use in a Geographical Information System, we examined relationships between forest cover and Eagle ecology at landscape and individual territory scales. Several territories were abandoned during the earliest phases of forest planting, but relatively few were apparently lost to later plantings. Territories with poorer breeding productivity appeared to be more vulnerable to abandonment than territories with better breeding productivity. At the landscape scale, temporal differences in breeding productivity were negatively related to the extent of forest cover, although productivity of individual territories showed no clear relationship with forest cover. Several territories with less than a 5% increase in forest cover experienced reduced productivity; however, territories least constrained by neighbouring pairs of Eagles showed an increase in productivity. Territories experiencing the greatest increases in forest cover showed a greater use of spatially separated nest‐sites by occupying pairs. Hence, pairs that were less constrained by neighbours appeared to compensate for loss of open habitat by shifting their territory‐use, whereas pairs that were more constrained could not compensate for open habitat loss and suffered reduced productivity (and, probably in some cases, abandoned the territory). We suggest that simple guidelines based on the extent and locations of habitat loss are inadequate when predicting effects on large territorial raptors such as Golden Eagles. Consideration should also be given to the ‘quality’ of a territory or occupying pair, as well as the extent to which territory‐use is constrained by neighbouring pairs or other ‘unsuitable habitat’ which may have been affected by previous episodes of open habitat loss.