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IBIS Abstracts
A selection of abstracts from Ibis prepared for the BOU by Dr Juliet Vickery
Kelp Gulls avoid siphonariid limpets because of repugnant
mucus
Davenport, D. 2001 Ibis 143 (April 2001), 304-306
Everyone knows that the main protection a limpet has from gulls is its
shell – or is it? Not for the Antarctic limpet Kerguelenella
lateralis. Its flimsy shell is barely big enough to accommodate its
body. Instead it relies on making itself highly unpalatable by exuding
copious amounts of white stringy mucus when attacked. The tactic is a
highly effective one if Kelp Gulls are anything to go by.
John Davenport from University College Cork studied the Kelp
Gulls in South Georgia where they have just two species of limpet to chose
from – Nacella concinna and K. lateralis. The limpets
occupy different shoreline locations. K. lateralis occurs in huge
numbers in shallow pools that are uncovered for long periods of time. In
contrast, N. concinna lives around the low water mark where it is
exposed only briefly. Despite being more accessible, observations and
careful examination of the contents of gull middens show K. lateralis
is never taken by Kelp Gulls. In fact, when small numbers of limpets were
laid foot up in the path of gull flocks K. lateralis was virtually
spat out in disgust and gentle prodding under a microscope shows why.
Whereas N. concinna simply retreats to its shell hastily K.
lateralis produces a mass of white stringy mucus. It’s an unusual
reaction and it reduces Kelp Gulls to a monotonous diet.
Associations of Crested Guinea Fowl Guttera pucherani ands
monkeys in Kibale national park, Uganda
Seavy et al 2001 Ibis
143 (April 2001), 310-312.
The tendency of some bird groups to associate with monkeys is well known,
especially in the neotropics. Insects disturbed by foraging mammals are
easy prey for birds perched nearby. Records of ground foraging birds
associating with arboreal monkeys are rare, but scientists from the
University of Florida, working in Kibale Forest in western Uganda, report
frequent encounters with Crested Guinea Fowl Guttera pucherani
associating with l’Hoest’s Monkeys Cercopithecus l’hoesti.
This unusual pairing has never been recorded before. For guinea fowl there
are probably rich pickings as soil and litter-dwelling arthropods are
disturbed when the monkeys come to the ground. The monkeys on the other
hand may benefit from the loud and raucous alarm calls of the guinea fowl
– a highly effective predator alert.
Nectar consumption of warblers after long-distance flights during
spring migration
Regine Schwilch, Rosita Mantovani, Fernando Spina & Lukas Jenni
Ibis 143 (January 2001): 24-32
The energy demands of long-distance migration are immense for birds such
as warblers. Migrants fuel their flight by catabolizing fat stores and
protein and often arrive at their destination with no trace of reserves
and greatly reduced breast muscles. To make matters worse digestive tract
is also reduced during the flight so although they must re-fuel fast the
avian equivalent of human pasta-packing is not an option. The solution is
a surprising one. Birds such as
Subalpine Warblers S cantillans and
Garden Warblers S. borin abandon their usual insect-based diet and
seek out a more readily absorbed and energy-rich food - nectar.
A group of scientists led by
Regine Schwilch from the Swiss Ornithological studied migrants on the
Tyrrhenian coast of Italy where birds arrive from North Africa having
crossed 500 km of open sea. For the first time they documented regular
exploitation of nectar of two native plants species by a range of European
migrants. The birds were adept nectar foragers. Garden and Subalpine Warblers,
Blackcaps S. atricapilla and Whitethroats S. communis
either ‘grazed’ small exposed drops of nectar from flowers of Ferula
communis or probed and drank nectar hidden at the base of flowers of
Giant Fennel Brassica fructulosa. Temporarily caged birds showed a
clear preference for nectar-like sugar solutions over mealworms especially
among birds with the lowest fat or muscle reserves.
Nectar is the perfect way to
re-fuel. It is readily available so birds can save on foraging time and
rest instead. The sugars it contains require no digestion so it is easily
absorbed by their much-reduced gut. In fact the sugar concentration of Brassica
is particularly high (40-70%) compared with nectar from other plants in
hot dry regions (20-50%) – all in all the perfect carbo-loading diet.
Food provisioning to nestlings in the Hoopoe Upupa epops: implications
for conservation of a small endangered population in the Swiss Alps
Jérôme Fournier and Raphaël Arlettaz Ibis 143
(January 2001): 2-10
The Hoopoe is a typical bird of traditionally cultivated landscapes. No
surprisingly it thrives in the relatively extensive agricultural
landscapes of southern Europe but in the intensively managed farmland of
western and central Europe the species is faring badly. Research in
southwest Switzerland has now provided vital ecological insights that may
assist the recovery of
Hoopoe
populations at least on a local scale.
Jérôme Fournier and Raphaël
Arlettaz studied nestling diet and foraging behaviour of birds breeding in
the Upper Rhone valley - an area of intensively cultivated plains and
hillsides of vineyards with small patches of steppe grassland and natural
forest. Nestlings were fed almost entirely on Lepidotera, mainly
caterpillars, and adult and larvae Molecrickets. However, the more
Molecrickets a chick received the higher its likelihood of surviving and
Molecrickets aren’t so easy to come by for most adult
Hoopoes. Careful
observations of foraging adults revealed that, whilst Lepidoptera were
gathered largely from the hillsides, Molecrickets came almost entirely
from the plains. This puts
Hoopoes in a catch 22 situation. Large trees
with natural breeding cavities, usually woodpecker holes, have been
virtually eliminated from the plains. Hoopoes are thus forced to nest in
the adjacent foothills and, as a result, adults must travel further to
feed on the good areas of the plains. This inevitable reduction in
provisioning efficiency is reflected in a decline in breeding success with
altitude (and hence distance from the plain). The authors suggest that
creating nesting sites on the plains might be one way to improve
Hoopoe
survival in the area. In the long term this requires planting hedges and
woodland but artificial cavities could provide a valuable short term
measure
Daily routines and predator encounters in
Yellowhammers Emberiza
citrinella in the field during winter
Ineke T. Van Der Veen Ibis
(July 2000) 142: 413-420
Winter is a tough time for small passerines that must build up reserves
during short days to see them through long cold winter nights. The larger
the fat reserve the lower the risk of starvation but the extra ballast
often reduces the birds speed and agility in flight making them easy
pickings for hungry predators. Theory predicts that birds should postpone
foraging until late in the day, minimising the time it is encumbered by
large fat reserves.
Contrary to predictions, in mid
winter Yellowhammers foraged on farmland at a constant rate throughout the
day. Ineke Van der Veen from the Department of population Biology in
Uppsala suggests this reflects severe 'time stress'at a time when days are
at their shortest and temperatures at their lowest. This is supported by
the fact that birds seem to sacrifice time spent on the look-out for
predators to devote more time to packing in the calories. Birds also
'sunbathed' immediately after the sun appeared above the trees - perhaps
using the sun's warmth to reduce their energy requirements.
These results highlight just
what a struggle it is for farmland birds to survive in winter - a struggle
made worse by the switch from the widespread switch from spring to autumn
sowing of crops. This has reduced the area of weed and seed rich stubble -
a vital foraging habitat for birds like the
Yellowhammer.
Influence of rodent density on nesting associations involving the
Bar-tailed Godwit Limosa limosa
Tore Larsen Ibis
(July 2000) 142: 476-481
Nest predation is often intense
for birds breeding in the arctic and subarctic especially in years when
alternative prey for nest predators, such as lemmings and small rodents,
are scarce. As a result birds, such as ground nesting waders, often breed
close to other more aggressive species to benefit from a 'protective
umbrella' they maintain around their own nests. For bar tailed godwits
breeding in northern Norway the two potential 'protectors' are whimbrel
and long-tailed skuas. The latter are extremely aggressive and so offer
the best nest protection but they also pose a threat because they commonly
take godwit eggs and chicks when rodents are hard to find.
Tore Larsen of Volda College,
Norway, mapped the location of nests of godwits and skuas in Finnmark
Northern Norway over seven years. Godwit nests were rarely found more than
200-300 m from nests of whimbrels or skuas - ensuring they lay well within
'protection patrol area'. However in years when rodents were absent
godwits nested much further away from skuas than in years when rodents
were plentiful. Larsen suggests godwits weigh up the costs and benefits of
associating with skuas by evaluating the rodent numbers. They may do this
either from their own encounter rate with rodents before laying or from
the distinctive flight behaviour of skuas when hunting rodents. However
they manage it, they are certainly discerning about the company they keep.
Lunar synchrony in the reproduction of the Moluccan
Megapode Eulipoa
wallacei (Megapodiidae, Galliformes)
Gillian Baker and Rene Dekker Ibis (July 2000) 142: 382-388
Megapodes have a pretty
minimalist attitude towards their eggs and young and the Moluccan
Megapode
is no different. It buries its eggs deep in the sand of sun-exposed
beaches and abandons them to be incubated by the sun and hatch unattended.
Unlike any other megapode, though, this species lays its eggs at night,
particularly at full moon. New research suggests this lunar-linked
behaviour may reduce the risk of predation for burrow digging adults that
literally have their head in the sand.
Most of the world's population
of Moluccan
Megapodes relies on two communal nesting grounds on the
islands of Haruku and Halmahera, Indonesia. Villagers, who harvest the
eggs for food, have long asserted that megapode activity varies with the
phase of the moon. Scientists, shadowing harvesters found nests were more
aggregated, and egg number and burrow depth peaked, after a full moon -
observations that fit with an anti-predation strategy. A digging adult is
very vulnerable to predators. At 500g it's too big a beakfull for
nocturnal raptors and there are no large carnivores mammals on the
Moluccas. The main threat is monitor lizards and pythons, neither of which
need light to hunt. On dark nights, when predators are difficult to see,
megapodes dig, surreptitiously, alone. On bright nights however predators
are more readily spotted especially with plenty of other wary excavators
close by. Communal nesting grounds experience rush-hour on these moonlit
nights and safety in numbers allows birds to spend longer on the job,
digging deeper burrows that afford the eggs added protection.
Major specimen fraud in the Forest Owlet Heteroglaux (Athene
auct.) blewiiti
Pamela C. Rasmussen & Nigel J. Collar Ibis (January 1999) 141: 11-21
A remarkable piece of
ornithological detective work has revealed a second major specimen fraud
among museum bird skin collections by Richard Meinertzhagen, this time
among the Forest Owlet Heteroglaux blewiiti (Ibis 141,
11-21. The species is known from central India and from just seven old
specimens. The most recent five include 4 collected by Davidson between
1880-83 in northwest Maharashtra and one purportedly collected in Gujurat
30 years later by Meinertzhagen. Meinertzhagen was one of the last great
British collectors and amassed thousands of skins in his lifetime.
However, recent documentation of specimen fraud by Meinertzhagen in
Redpolls (Ibis 135: 320-325) has prompted detailed examination of
any of his specimens including his 1914 Forest Owlet. Detailed scrutiny of
this owlet, including x-rays, reveals the remarkable lengths to which this
collector must have gone to pass this Owlet off as one he had collected.
The specimen had been extensively re-made through compressing the neck,
treating it with a solvent to remove oils that seep out of skins over
time, twisting and re-setting the legs, and removing much of the bone in
the skull to reposition the bill.
Additional evidence that
something was amiss comes from Meinertzhagen's usually meticulous diaries.
These contain no reference to him having left Bombay on a collecting trip
at the time the skin is dated. He has never recorded a Forest Owlet in his
own register and has never published on the specimen despite its extreme
scarcity. Furthermore, whilst the specimen bears little resemblance to any
of the verified Meinertzhagen skins it does bear hallmarks of Davidson's
rather unique preparation style. The final twist in the tale is that a
Davidson specimen is inexplicably missing from the British Museum of
Natural History collection. Taken together these findings comprise
overwhelming evidence for the fact that Meinerzthagen stole the fifth
Davidson forest owlet and remade and relabelled it to conceal its origin
something which has compromised the geographic and temporal record of this
critically endangered bird.
New Species of Barwing Actinodura (passeriformes: Sylviinae;
Timaliini) from the Western Highlands of Vietnam
Jonathon C. Eames, Le
Trong Tria, Ngyuen Cu & Roland Eve Ibis (January 1999) 141: 1-10
Fieldworkers from the Birdlife
International Vietnam Programme and Forest Inventory and Planning
Institute of Vietnam have discovered a new species of Barwing during the
first ornithological surveys of proposed nature reserve Ngoc Linh, in the
Western Highlands of Vietnam. In general, species of the genus have two
defining characteristics - transverse barring on the remiges and retrices
and a crest. However, this new species has three characteristic features
otherwise unknown in the genus - a distinctive black crown, bold streaking
on the throat, extensive black margins on the primaries and secondaries
which make the wing appear black and unbarred. Although only reported from
the Kon Tum province, the scientists suggest it is likely to occur widely
in the montane evergreen forests from c 1100-2400 m in the Western
Highlands and in adjacent Laos. It has been aptly named the Black-crowned
Barwing, with the Latin name afforded it, Actinodura sandangorum,
meaning of the Sodang people in honour of the Sodang tribe who share the
forest of Ngoc Linh.
Mortality and survival of African
penguins Sphenscus demersus
involved in the Apollo Sea oil spill: an evaluation of rehabilitation
efforts
Underhill, L.G. et al Ibis (January 1999) 141, 29-37
A spate of papers have
suggested that attempts to rehabilitate oiled seabirds are futile because
the survival of released birds is extremely low. New results from a South
African study provide welcome evidence that all is not doom and gloom for
oiled birds that have been cleaned and returned to the wild. The South
African National Foundation for the Conservation of Coastal Birds (SANCCOB)
gathered around 10,000 oiled African Jackass Penguins Spheniscus
demersus when the bulk ore carrier Apollo Sea sank near Dassen island,
South Africa in June 1994. Of these, 5213 were released between July and
September of the same year, 4076 with flipper bands. This was followed by
two years of extensive searches of beaches and breeding colonies to
re-locate banded birds. The mortality rates of marked, free-living, wild
penguins, banded as part of a wider study, suggest very few birds had died
at sea before the rescue work and 65%of released birds made the transition
from the rescue centre to the wild successfully within two years of their
release. Overall the results suggest no major pre or post release
mortality. The scientists suggest that the success of penguin
rehabilitation procedure could be improved by concentrating on the period
when most mortality takes place - from oiling to when the birds have been
in the rescue station for about 48 hours - when rapid capture,
stabilization and transport to the rescue centre is crucial. Despite this
they also warn that prevention is better than cure and the objective must
still be to reduce the volume of oil that enters the sea
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