Cliff Ledges Research Articles

First North American Nesting and Occurrence of Haliaeetus albicilla on Attu Island, Alaska

The nearctic range of White-tailed Eagles (Haliaeetus albicilla) is listed as casual in the Aleutian Islands, Alaska (Attu, where probably breeds, Unalaska), in eastern Greenland and off Massachusetts, near Nantucket Lightship (AOU 1983). The species breeds only in western Greenland in the nearctic; a breeding report from Baffin Island has not been confirmed (AOU 1983). Reference in the AOU Check-list to H. albicilla breeding at Attu is based on data presented herein. We discovered an active aerie of this species on Attu Island (52049'N, 173010'E) in 1982. We have numerous observations of four individual H. albicilla there in May to September, 1977 to 1986 (summary follows). These observations and the nest site are all from the river valleys and coastline at the east end of Attu Island. We located the active nest in Temnac Valley on 25 May 1982 after watching both adult eagles take turns sitting in a rocky depression on a cliff ledge. On subsequent trips to this site in 1982 (31 May, 4 June) both adults were seen attending to a single downy chick. Photographs of the nest site are on file at the University of Alaska Museum (UAM). The same nest was active in 1983 with a single chick present. This chick was fledged and feeding on pink salmon (Oncorhynchus gorbuscha) with the adults along the Temnac River in September 1983. This nest has not been active since 1983; only one adult eagle has been recorded at Attu since 1983. The nest site was located on the north side of Temnac Valley, 2.7 km from the Temnac River mouth (and salt water) at approximately 80 m above sea level. The nest cup sat on a fractured rock ledge 20 m up the southeast face of a rock pinnacle. This pinnacle stood immediately in front of a south-facing 40-m high cliff face. A heavily vegetated 350 talus slope stretched from the pinnacle base to a point close to the river, roughly 30 m away. With a rim about 10 to 15 cm high on the outside, the nest was approximately 1 m in diameter. The wellpacked cup consisted of kelp (probably Laminaria), fronds and rachis of Athyriumfilix-femina, and Elymus arenarius. Stalks and a few umbel heads of Heracleum lanatum were included in the rim. This is a similar to contents from Aleutian nests of Bald Eagle H. leucocephalus (Murie 1959).

RELATIONSHIP BETWEEN MORPHOLOGICAL ADAPTATION TO GRAZING, CARBON BALANCE AND WATERLOGGING TOLERANCE IN CLONES OF DACTYLIS GLOMERATA L.

SummaryClonally‐propagated individuals of Dactylis glomerata L. derived from two contrasted habitats, respectively, moist soil with no grazing and drought‐prone soil under intense grazing, were tested for tolerance of waterlogging in soil culture. The clone of dry soil unexpectedly proved much more tolerant than the clone of moist soil. Measurements of 24 populations of D. glomerate grown in an experimental garden showed that the grazing pressure in the original habitat is reflected very strongly in the morphology of the garden‐grown plants. Adaptation to grazing comprises a short and narrow‐leaved, prolific tillering habit with production of very short inflorescences. Heavy grazing, or the cutting regime imposed in the waterlogging trial, is likely to do more damage to the upright, long‐leaved morphs of the ungrazed site. Measurements of carbon balance in intact plants and in defoliated tillers support this interpretation and also suggest that the larger oxygen consumption of the massive leaf bases of the ungrazed form might limit root penetration in oxygen deficient conditions. The greater length of roots in the dry soil clone is also discussed as a possible adaptation to water shortage in its cliff ledge habitat.

Reproduction du Grand Cormoran (Phalacrocorax carbo) et du Cormoran à aigrettes (P. auritus) aux îles de la Madeleine, Québec

The Great Cormorant (Phalacrocorax carbo) and the Double-crested Cormorant (P. auritus) on the Magdalen Islands (Québec) nest in different types of habitat; all Great Cormorants nest on the ground either on cliff ledges or on the flat tops of rocky islands, while all Double-crested Cormorants nest in coniferous trees. No mixed colonies were seen in 1977 and 1978. Most Great Cormorants laid their eggs some 10 days before the Double-crested Cormorants. The mean clutch size was 4.4 for the Great Cormorant in 1978 and 3.2 and 3.6 for the Double-crested Cormorant in 1977 and 1978. The hatching success was similar for both species, 69.2% for the Great Cormorant in 1978 and 74.5 and 71.8% for the Double-crested Cormorant in 1977 and 1978. Great Cormorant chicks had a higher mortality rate mainly during their first 2 weeks of like. This resulted in a similar ratio of young fledged for both species of cormorant, about 2.0 fledglings per clutch for the Great Cormorant and 2.1 and 2.4 fledglings per clutch for the Double-crested Cormorant in 1977 and 1978. The greater mortality rate of young Great Cormorants reflects differences in nesting sites' conditions.

BREEDING BIOLOGY OF THE BOOTED EAGLE IN SOUTH AFRICA

Summary Steyn, P. & Grobler, J. H. 1981. Breeding biology of the Booted Eagle in South Africa. Ostrich 52:108-118. The Booted Eagle Hieraaetus pennatus is a breeding visitor to the Cape Province of South Africa, wintering mostly in Namibia on present knowledge. Palaearctic birds probably also reach the Cape but arrive later. Two nests in different localities in the Cape were studied. The birds breed soon after arrival. Both sexes build the nest on a cliff ledge. Incubation, which lasts 40 days, is done mostly by the female. The female spends most of her time on the nest during the first four weeks of the nestling period, but considerably less time thereafter. The male provides nearly all the prey until near the end of the nestling period, and helps to feed the young. Details of nestling growth and behaviour and of parental care are given. The nestling period was 50 and 54 days in two cases. Post-nestling dependence is about two months. Prey preferences in the two study areas were very similar: 54% birds, 33% lizards and 13% rodents. Breeding biology in South Africa is basically the same as that of Palaearctic populations, with the main differences being the habitat and cliff nest site.

Tree-Nesting Peregrine Falcons in British Columbia

Records of Peregrine Falcons (Falco peregrinus) nesting in trees, either in nests built by other large birds or in hollow tree trunks, have been well documented in parts of the Old World (Thomasson 1947, Dement'ev and Gladkov 1951, Fischer 1968, Mebs 1969). In North America, a few such records are available from Alaska and the central United States, but the details are obscure (Hickey and Anderson 1969). This paper provides information on six tree aeries located on offshore islands, found during a survey of seabird nesting colonies along the northern coast of British Columbia in June and early July 1976. Because of the peregrine's sensitivity to human disturbance and because of recent public concern for the species, we do not give exact aerie locations but have filed them (see Campbell and Stirling 1971) with the British Columbia Provincial Museum (BCPM). We discovered the first tree nest of peregrines on 20 June. While searching through dense undergrowth along the shores of a small wooded island for nesting alcids, we encountered an agitated adult female peregrine calling from the top of a dead Sitka spruce (Picea sitchensis). The shore sloped gently towards the sea. Few cliff ledges were available for nesting falcons, but two abandoned Bald Eagle (Haliaeetus leucocephalus) nests, about 25 m apart and 34 m from shore, were present near the top of the island. In one nest, about 18 m above ground, a large, white, downy, young falcon sat near its edge. We could not reach the aerie (BCPM Photo No. 454) so exact nest contents were not determined although we did not observe other nestling activity. Prey remains below the nest included Rhinoceros Auklet (Cerorhinca monocerata), Cassin's Auklet (Ptychoramphus aleuticus), and Pigeon Guillemot (Cepphus columba), none of which nested on the island. The nearest seabird colony (storm petrels and auklets) was about 100 km to the SE.

Tidal rhythm in a seabird.

GUILLEMOTS (Uria aalge) breed on cliff ledges in densely packed colonies often numbering many thousands of pairs. About 25% of the British population of these birds nests in Orkney1, where their proximity to North Sea oil developments makes it important that the numbers breeding are continuously monitored to check for any adverse effects. One of the difficulties in estimating the breeding population is that the numbers present on cliff ledges show considerable variation, particularly before egg-laying2. The data presented here were collected on the island of Copinsay, Orkney, between April 20 and May 13, 1976 with a view to determining the reasons for these fluctuations. They demonstrate the clear effect of a tidal rhythm, a phenomenon previously described for birds which feed close inshore3,4, but not apparently for any species which feeds in deeper water, though Tuck5 makes passing reference to the possibility of such an effect at some of the guillemot colonies which he studied in Canada.

Observations on the Subgenus Argas (Ixodoidea: Argasidae: Argas), a. (a.) lowryae. New Species, Parasitizing Cave-dwelling Kestrels in the Nullarbor Region of Western Australia1,2

Argas (Argas) lowryae n. sp. is described from nymphs and larvae taken from kestrels, Falco cenchroides Vigors and Horsfield, from adults reared from some of these nymphs, and from nymphal and adult specimens found on walls near the entrances of large underground caves in which the kestrels breed in the Nullarbor region of Western Australia. Each postembryonic stage is easily distinguished from those of A. (A.) falco Kaiser and Hoogstraal and A. (A.) lagenoplastis Froggatt, the only other members of this subgenus known from Australia, and from related species in Asia, Europe, Africa, and America. The host, F. cenchroides, is also parasitized by A. (A.) falco in Western Australia but in a habitat and ecological environment (cliff ledges in the semiarid mulga zone) differing from that of A. (A.) lowryae.

Some Aspects of the Ontogeny of Cliff Nesting Behaviour in the Kittiwake (Rissa Tridactyla) and the Herring Gull (Lar Us Argentat Us)

This study analyses the behavioural peculiarities that enable Kittiwakes to raise their young on narrow cliff ledges. For comparison parallel studies were made on both Cliff and ground nesting Herring Gulls and some aspects of the ontogeny of the behaviour involved were investigated. 1. The Nest Cup. Kittiwake chicks and to a lesser extent, cliff nesting Herring Gull chicks, rarely leave their nests. This is not because they lack mobility, as was shown by a number of experiments, nor is it consequent upon nest construction. My observations show that the chicks' safety is due to a complex of behavioural characteristics. 2. Parental Behaviour. Chicks are brooded continuously for the first day of life but after this the Herring Gull tends to brood spasmodically and far less frequently than the Kittiwake. Experiments showed that young chicks were not inhibited of moving in darkness but this tendency would probably be checked by parents brooding. Kittiwakes are loathe to leave their broods unguarded even during a disturbance or when incited to fight. Herring Gulls are more easily frightened into flying from their nests and readily leave their chicks to enjoin a fight. Kittiwakes always alight at the nest and feed their chicks from their throat. Herring Gulls feed theiti chicks anywhere on their territory and, particularly when a feeding call is given, chicks run to them. This behaviour endangers cliff nesting chicks, however they appear to learn, within their first week of life, not to attempt to approach a calling parent but to wait until it flies to the nest. 3. Chicks Behaviour in the Nest. Cliff nesting Herring Gull chicks behave very like Kittiwakes in that they rarely stand for long periods and their main orientation is toward the wall. But unlike Kittiwakes they are vulnerable whilst wing flapping because more than one chick may flap at a time. They are also more vulnerable when disturbed for although some 'freeze' others run and may jump off the ledge. 4. Chicks reaction to a Visual Cliff. The jumping of the Herring Gull occurs despite the fact that under less disturbing Conditions many show an avoidance of the cliff edge. But their response is not as dramatic as that shown by the Kittiwake chicks who give a perfect avoidance response. 5. Chicks reaction to a Tactile Cliff. The Kittiwakes showed a less perfect edge avoidance when elicited by tactile cues alone, and it was not certain that Herring Gull chicks could detect edges at all on tactile cues alone. 6. Chicks reaction to a Wall. Although all cliff nesting chicks orient toward a wall when in their nest, Herring Gull chicks did not appear to be attracted to a wall and only very young Kittiwake chicks were attracted to a wall which they would approach and snuggle against. 7. The ontogeny of some of the behaviour studied. Because chicks taken from the natural nest site might have already g-ained and profited from experience, eggs were hatched in an incubator and chicks raised under one of three conditions. One group were raised in a situation similar to ground nesting conditions, a second in cliff nest like conditions, whilst a third group were reared in perspex boxes, suspended above the ground, so that they had the visual stimuli of an abyss combined with the 'wrong' tactile stimuli. On the whole the Kittiwake chick's responses are remarkably independant of, and resistant against experience, for the full repertoire of responses studied were present in all these incubator hatched chicks, except the tactile anti-cliff response, which did not develop in one-day old chicks who had no experience of an edge. In the Herring Gull the story is somewhat different. Differences between cliff and ground nesting Herring Gulls must be due to their upbringing as was indicated both by observations on chicks from eggs that had been exchanged between cliff and ground breeding sites and from the laboratory experiments. Also their visual anti-cliff response which is less than perfect showed a phenotypic improvement in laboratory tests.

The ecology of cliff ledges on Tarmachan Nature Reserve, Perthshire

The ecology of cliff ledges on Tarmachan Nature Reserve, Perthshire

ADAPTATIONS TO CLIFF‐NESTING IN SOME ARCTIC GULLS (LARUS)

SUMMARYVarious aspects of the breeding of three gulls, Larus thayeri, glaucoides and hyperboreus, which nested in colonies both on cliff ledges and on level ground in the eastern Canadian Arctic, were compared with those of the ground‐nesting L. argentatus and the cliff‐nesting Rissa tridactyla. As the result of adaptation to cliff ledge nesting, many aspects of the breeding biology of R. tridactyla were strikingly different from those of the ground‐nesting European L. argentatus, but the behaviour of L. thayeri, glaucoides and hyperboreus clearly spanned these differences.Cliff‐nesting individuals of thayeri and glaucoides were most like Rissa; ground‐nesting individuals of these species were most like argentatus. L. thayeri was more like Rissa than was glaucoides. With but few exceptions, both cliff‐ and ground‐nesting individuals of hyperboreus were most like argentatus. The factors responsible for the intra‐specific differences between cliff‐ and ground‐nesters of thayeri and glaucoides are not clear. Limited gene exchange between cliff and ground colonies occurs.Because of physical features of the nest, first‐laid eggs were more liable to fall from ledges than second or third eggs. L. thayeri and glaucoides have evolved separate mechanisms to cope with this problem. Egg shape was multimodal in thayeri and glaucoides. Long pyriform eggs were less liable to fall from ledges than eggs of other shapes. L. thayeri laid more long pyriform eggs as first eggs than did glaucoides. L. thayeri lost fewer eggs than did glaucoides, but glaucoides replaced all lost eggs while thayeri did not. Delayed follicular atresia provided glaucoides with insurance of egg replacement. In thayeri, accessory follicles were reabsorbed after the first egg was laid; in argentatus, after the second egg, and in glaucoides after the third egg.At the approach of a predator, it was advantageous for cliff‐dwelling chicks to remain motionless but for ground‐dwelling chicks to flee their nests and to hide. Among the cliff‐nesters, the “freezing in place” reaction of chicks was best developed in thayeri, to a lesser extent in glaucoides, and least in hyperboreus. Among the ground‐nesters, chicks of glaucoides and hyperboreus behaved like those of argentatus and fled their nests when disturbed, but chicks of thayeri froze like their cliff‐dwelling siblings. Reciprocal transfers of eggs and chicks between cliff and ground colonies indicated that in argentatus, glaucoides and hyperboreus, the factors determining a chick's reaction to disturbance came into play between hatching and the eighth day. In thayeri, the reaction appeared to be effectively innate. Chicks of glaucoides showed a greater predisposition to this behaviour than chicks of argentatus after both had received identical experience on cliff ledges.In thayeri, stereotypy of the freezing reaction has probably been a factor limiting the colonisation of areas where cliffs are scarce but predators present. In argentatus, lack of perfection of this behaviour (compared to glaucoides and thayeri) has probably been a factor preventing argentatus from attaining cliff ledges. L. hyperboreus, although nowhere abundant, is a widespread species nesting on level ground and on cliff ledges but lacking the modifications observed in glaucoides and thayeri; this is due to its size and aggressiveness, the fact that it picks nest‐sites before glaucoides and thayeri arrive in the colonies, and that on cliffs it chooses the largest and most level ledges.

Determinants of Cliff Edge and Escape Responses in Herring Gull Chicks in Nature1)2)

AbstractHerring gull chicks from nests on a) cliff ledges and b) vegetated plateaus showed different types of escape and edge response when tested on an elevated platform. The birds from cliff sites, though bolder at the platform edge, were more reluctant to jump. Those from the plateau nests leapt to the ground with relatively little hesitation. Chicks from cliff eggs, hatched and reared in the plateau by foster parents, resembled native plateau chicks in their escape responses while chicks of plateau origin reciprocally transplanted to and reared on cliff sites showed the reluctance typical of cliff chicks. The posssibility of two genetic types reproductively isolated on the two breeding situations is thus essentially eliminated. The likelihood of a stable genetic polymorphism is considered and tentatively discarded as less plausible than an explanation based on learning. Although conditions favorable for simple instrumental conditioning along divergent lines are present in the two rearing situations, a theory is favored which attributes the divergence to major differences in the amount and variety of experience afforded by the two environments. Modest support for this theory is provided by experiments in which plateau chicks confined by fencing to the immediate nest vicinity tended to resemble the naturally deprived cliff chicks in their reluctance to jump. In conclusion the concept of species-characteristic responses is considered inapplicable to the cliff edge and escape patterns of herring gull chicks except as it incorporates recognition of a determining role in factors of the rearing environment.

THE BREEDING BIOLOGY OF THE SHAG PHALACROCORAX ARISTOTELIS ON THE ISLAND OF LUNDY, BRISTOL CHANNEL

SUMMARY1. In the 4 years 1454–1957 the breeding population of Shags on Lundy appeared to he static. Most of the nest‐sites were used each year. Mortality was deduced from the re‐use of old nest‐sites and the return of colour‐marked birds.2. Most of the clutches were started during a period of 3 to 4 weeks in each year but dates varied by as much as 1 6 days in different years.3. Different types of ncst‐site and nest‐material are used on different parts of the island. Larger nests were more successful than smaller ones.4. The mean‐clutch size for the five years 1954–1958 was 307, varying annually by us much as 0–4 egg. Clutch‐size decreases with the advance of the season.5. Incubation starts with the second egg in c/3 but a day or more later in c/4.6. Hatching success 1954–1957 varied only between 69 and 73%. Infertility was the mam cause of hatching failure.7. Eggs were weighed and measured in 1957 and 1958. In each year the larger clutches contained larger eggs than the smaller clutches. The mean weight of eggs was greater in 1957 (when clutches were bigger) than in 1958. This was due to a higher specific gravity.8. Fledging success was 90–95%, except in 1956 when it was 67%. The heavier losses in this year appeared to be due to food shortage. Most chick losses occur in the first ten days.9. The growth of chicks was studied in 1957. Male chicks can frequently be differentiated when 30 days old by their heavier weights. The fourth chick in a brood is normally below average weight during the first half of the fledging period.10. Some marked juveniles remain on the island up to 50 days after leaving the nest. During this time they show partial dependence on their parents.11. Later clutches are less successful than early clutches. Nests situated on narrow cliff ledges were less successful than nests at other sites.