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High
and Dry in Morocco
I
went to Morocco in April this year with Alan Hayden, Leo Pyke, Mike McKee and
Chris Turner to visit the 'high' Atlas Mountains and the 'dry' stony desert areas
stretching out towards the Sahara proper. We flew from Gatwick and arrived very
late in Marrakech where there was a strike by the local taxi drivers. A shady
character emerged from the shadows and ushered us to his private car, which unfortunately
turned out to be a rather small Fiat. It was cosy, to say the least, for the five
of us but thankfully it was only a very short drive to the Ibis Hotel where we
were staying.
We ticked
off the first birds of the trip over breakfast, namely Pallid Swift, Little Swift
and House Bunting and then headed back to the airport (this time in two taxis)
to pick up our pre-booked, roomy 4x4. Mike, Chris and Alan started taking photos
of the birds around the airport, whilst waiting for the car hire desk to open,
which attracted the attention of airport security. We were lucky to get away without
getting our optical equipment confiscated.
The
Atlas Mountains rise to over 10,000 feet and their snow-capped peaks are visible
from Marrakech, 70 kilometres away. Driving through the city outskirts were saw
White Storks by the road and Bee-eaters on the wires. We were heading for Oukaimeden,
which is a ski resort in the High Atlas. At lower altitudes the mountains are
lush and green with areas of farmland set among woodland and scrub. Here we found
the 'ultramarinus' race of Blue Tit, which is bluer and brighter that those in
Britain and the 'africanus' race of Chaffinch, where the males have green backs
and much paler bellies than British birds. The woodlands are also home to Levaillant's
Green Woodpecker, which is very like Green Woodpecker, but with a black moustache,
rather than a black mask on the face. And it's 'tick' unlike the very distinctive,
but un-tickable Blue Tit and Chaffinch. At higher altitudes the trees faded out
revealing Moussier's Redstart and Black Wheatears hopping about the bare rocks.
€
The
birding was excellent all around Oukaimeden with plenty of mountain species including
Rock Sparrow, Blue Rock Thrush, Rock Bunting, Black Redstart, Chough and Alpine
Chough. Unbelievably as we queued for the ski-lift a Lammergeier flew down the
valley and virtually over our heads only to disappear without trace. The lack
of oxygen made trekking around the peaks hard work, but there were plenty of Atlas
Horned Larks and a few Northern Wheatears of the Seebohmi race, with the characteristic
black face.
We returned
to the base of the ski-lift at 6am the next day to look for one of our key target
species, Crimson-winged Finch, before the crowds arrived. All of us, except Alan,
clambered over the slopes in search of these birds, only for Alan to find one
on the ski-lift office roof! It was soon joined by several other birds, which
posed obligingly to have their pictures taken.
We
left soon after to cross the mountains and head for the desert. We stopped periodically
en route and picked up species such as Short-toed Eagle, Booted Eagle, Southern
Grey Shrike, Tristram's Warbler and Trumpeter Finch. We had booked to stay overnight
at Le Soliel Bleu, just outside Boumalne du Dades, which much to Alan's dismay
served no alcohol.
We
all woke with clear heads the next day to bird the famous stony desert area around
the Tagdilt Track from 6.15am onwards. The area was brilliant with plenty of Desert
and Red-rumped Wheatears, Temminck's Horned Larks, Cream-coloured Coursers and
just a couple of Thick-billed Larks. We headed off in the afternoon taking in
the Blue-cheeked Bee-eaters at the well-known colony near Jorf, before reaching
the Desert Inn near Merzouga.
Much
of Morocco is 'stony' desert, but close to Merzouga are the Erg Chebbi dunes.
Rising to 150 metres, these sand hills fulfil most people's expectations of what
a true desert should be - you really feel like you are on the edge of the Sahara
proper. The area is also excellent for birds. Migrants pass through the hotel
grounds including Nightingales and Sub-alpine, Melodious and Bonelli's Warblers.
We were also lucky enough to see Egyptian Nightjar flying over the pool at night!
Outside the open desert is good for Spotted and Pin-tailed Sandgrouse, Hoopoe
Lark and, around the various 'kasbah' buildings, Desert Sparrow. The scrubby wadis
in the area are also good for Desert and Spectacled Warbler.
One
'kasbah' style hotel complex is known as Café Yasmina and every few years
large seasonal pools form close to the buildings, bringing a wide selection of
wetland species to the desert. We added Black-winged Stilt, Kentish Plover, Squacco
Heron and Marbled Teal to our lists. The lakes and surrounding scrub also attracted
migrants such as Yellow Wagtail, Redstart, Sedge and Olivaceous Warbler.
On our way back, we stopped
off at a site for Eagle Owl near Rissani. The site is well away from any road
and although a 4x4 can take you some of the way, you also have to walk. The owls
inhabit caves and crevices in a seemingly never-ending inland cliff-face in the
middle of the desert and we thought that finding them would be difficult.
Fairly
shortly after arrival we managed to find a Brown-necked Raven gliding along the
cliff-face, but the owl proved elusive. Eventually we caught sight of something
large make a very short flight on the cliff face and we rushed over to check it
out. Sure enough it was the owl, which just sat there in the open giving excellent
views.
Only as we walked
away did we notice some stones arranged in the sand spelling out the words 'EAGLE
OWL', with a big arrow, pointing at the very point on the cliff face where we
had been looking. Slightly further on there were some more stones setting out
the letters 'LGRE' - that man (Lee Evans) certainly knows how to make his mark!
I
cannot recommend Morocco highly enough. It has a great selection of birds; fantastic
scenery and the locals are pretty friendly. If you want to see and hear more why
not come along to the slide show I will be giving for CHOG at 7.30pm in the Hengistbury
Head Centre on February 8th 2008? A good selection of bird photographs from the
trip also appears on Mike's website www.michaelmckee.co.uk.
Trevor
Warrick -Photographs © Alan Hayden
This Article was published
in the Dorset Bird Club's Newsletter June 2007
Ringing
on the Weymouth Reserves - a short note
There
has been a long, if interrupted, history of ringing at the RSPB's Radipole Lake
reserve and, with no ringing takin place on the reserve for getting on for a decade,
I have long wanted to re-establish a regular ringing programme here, not simply
because these reserves are, in themselves, fascinating and rare places but, placed
where they are, and with well established ringing programmes at Abbotsbury and
Portland Bill, they represent an obvious gap in that network and, given there
remains much we can still learn about how birds use this amazing area, these reserves
are well situated to help us in that quest.
I
think there is an old saying that goes something along the lines of 'the longest
journey starts with a single step'. Well, this year, at Radipole, that first step
(albeit a very small one) was taken by the reserve staff and volunteers and a
summer ringing programme was carried out. It was, as perhaps befits a first step,
a slow, timid and unsure start, but it gathered pace and confidence as the season
progressed and the data we have gathered, albeit small scale (as yet) will allow
us to improve what we do, and hence improve the information we gather, in future
years.
In total
we ringed 510 birds, of 20 species, including a rather paltry 7 bearded tits (more
of which later) a few hirundines and, of course, one aquatic warbler but, not
surprisingly, the other reedbed warblers featured largest amongst the birds caught,
with 303 Sedge Warbler (90% of which were juveniles) and 142 Reed Warbler (60%
of which were juveniles). Although the data are small, so we must be careful in
drawing too many conclusions from them, but it is interesting to ponder the difference
in the age classes of these birds.
Bull
and Morgan suggest the reedbeds here are used by c2,500 Reed Warblers and 6-10,000
Sedge Warblers during any one autumn. From this one might well expect to find
a greater number of sedge warblers (which we did, but not in the same ratio) and,
given that one expects to catch more juveniles in autumn, we should expect most
birds to be young ones (which, for sedge warblers, they were). I do not know,
but I suspect the greater proportion of adults in the reed warbler numbers reflects
the breeding population. As the data we gather builds it will be interesting to
see if/how that picture changes.
It
is also interesting to look at the habitat mix within which we were catching the
birds. In the same way that fashions change on the high street, ideas about how
to manage specific habitats change as we learn (or, in many cases, re-learn!)
important lessons and I feel this has particularly been the case with reedbeds.
Two or three decades ago the 'style' for reedbeds was great expanses of swaying
reed with little or no variation across large areas, resulting in large homogenous
vegetation blocks. Now we realise that, as with many other habitats, it is variation
that is the key and, perhaps, the records from the two sets of nets we put up
back that up.
One
set of nets was in the middle of a large homogenous block of reed. In truth the
only structure in the that particular block of reed was the ringing ride itself!
The second set of nets was on the edge of a rich mosaic of habitats, with reed,
sedge/rush beds, open water and wet grassland all around. As if to prove the point,
the second site had 14 (yes fourteen!) times the capture rate, per foot of net,
than the reedbed site, and for the same degree of effort - do you need any more
evidence that structure and variation in reedbeds is important!
I
mentioned earlier that we did not catch too many bearded tits. It has often puzzled
me where our beardies go and how our population fits in to the Dorset scene. There
have, in the past, been recoveries from Farlington Marshes and Great Salterns
Lake (Hants), Lytchett Bay (Dorset), Berrow (Somerset), Thurlestone (Devon), Sittingbourne
(Kent) and, excitingly, some from the Netherlands. Most, but not all, of those
recoveries were the result of ringing programmes at those sites. That limits the
chances of birds being recorded so, as has been done in the past, we hope to re-establish
a bearded tit project, using colour ringing, so that we can ask reedbed sites
to keep an eye out for 'our' birds and try and gain a better understanding of
where they are going to. We hope to be able to concentrate this effort on the
autumn, pre-erruption flocks, so gathering as much information about our population
as we can - time will tell, but we hope to be able to report more at a later date.
Some
statistics suggest that less than 1 in 100 birds ringed will ever be seen again
(hence the need to ring large numbers if you are ever to get meaningful data)
so we were rather excited to catch seven birds which were already ringed. At least
one of these was a 'Radipole' bird, a reed warbler that was first ringed here
nearly 11 years ago, making it a very old bird indeed! Three young sedge warblers
ringed elsewhere were also very nice, one from Abbotsbury, one from Leighton Moss
(Cumbria) and one, ringed some 621 km away, in Fife, just 7 days earlier! Star
of the show though has to be the aquatic warbler we caught in August, it was re-caught,
the next morning, in Seine-Maritime, France, some 234 km away! This is only one
of a handful of Aquatics ringed in this coutry that have been recovered elsewhere
so, as you can imagine, we are rather chuffed.
Finally,
at each ringing session we re-caught birds we had ringed on previous sessions
(in small numbers) an exercise that can be helpful in establishing population
estimates. Interestingly though, with one exception, all the birds re-caught were
re-caught in the nets they had first been caught in (if you see what I mean),
suggesting little or no exchange between the two sites, even though they were
only a few hundreds of yards apart as the warbler flies. What was quite simply
magical though was that on the day we caught our first young sedge warbler which
we knew had been born elsewhere, as it was already ringed, we stopped re-catching
our own birds, a clear indication that migration had truly started.
We
have much to (re)learn about how 'our' birds uses these reserves and how they
fit in to the larger picture, nationally and internationally. The first step has
been taken, and, as our restoration and long term management plans are implemented
it will be interesting to see how that picture evolves. We will, of course, keep
you posted, let's hope the information keeps flowing as well as it has this year!
Nick
Tomlinson
This
article was published in Dorset Bird Club's July 2003 newsletter.
TWENTY
PREDICTIONS FOR THE DORSET LIST
Guessing which will be the next bird to added to the Dorset list has been a constant
source of amusement. To get a broad opinion of likely candidates, I contacted
23 active Dorset birders, of which 18 replied. Each was asked to list, in order
of likelihood, the next ten species that they considered would be 'New for Dorset'.
Subspecies that
are likely be promoted to full species status in the near future were included
(e.g. Caspian Gull), but not those that have already occurred (like Hooded Crow),
even though they will be technically new to the Dorset list when upgraded to specific
status. I chose to exclude Kumlein's Gull as it seems highly unlikely that it
will be given specific status and Booted Eagle, as a claim for Dorset has already
been submitted and the bird that toured Ireland and the south-west appears destined
for Category D.
Each
correspondents number one species was awarded 10 points, the second 9 and so on.
In the account, the accumulated points for each species is given, plus the number
of the 18 correspondents that chose it. A total of 49 species were mentioned,
the first 20 of which are detailed below.
1st Citrine Wagtail
(140 points, 17/18) The clear winner with 78% of the available points. Breeding
from western Russia eastwards across the mid latitudes of Siberia, the range has
been spreading slowly westwards in recent years. Late Aug - mid Oct occurrences
are the norm. Up to 1998 there were 118 records in Britain including a couple
of long stayers at Farlington, indeed 2 occurred in Christchurch Harbour in 1966
in the days when it still languished in Hampshire. Although one may make a brief
appearance at one of the headlands, a long stayer is most likely to be found at
a wetland like Stanpit or Lodmoor.
2nd
Marsh Sandpiper (134 points, 15/18) I totalled up the species scores on 7th
April just before I spent a week in Scotland. To my amazement this species was
discovered at Stanpit a mere 3 days later (and fortunately remained long enough
for me to see it the next weekend). With a range from south-east Europe across
Asia, Marsh Sand has been recorded 101 times up to 1998, mainly in the east but
also in all south coast counties except Dorset and Cornwall. Records span from
mid Apr to early Oct, the Stanpit bird must be one of the earliest on record.
3rd
Caspian Gull (104 points, 12/18) As the BOU has yet to accept Yellow-legged
Gull as a full species, it may seem strange that we are considering its eastern
counterpart as a potential addition to the Dorset list. However Caspian Gull does
differ in morphology, display, choice of nest site and biochemistry and looks
to be awarded specific status soon. Clearly our correspondents were impressed
with its credentials and awarded it the Bronze medal. It seems that a proportion
of the population leaves the southwest Asian breeding grounds to winter in northern
Germany and the Netherlands. An extrapolation of this route will bring birds to
East Anglia and the reservoirs of the Midlands, which indeed is where most records
have occurred. Undoubtedly one will be found in Dorset, presumably by a skilled
gull enthusiast in a well watched area like Corfe Mullen tip, Holes Bay or Radipole,
but they are unlikely to become anything but a major rarity. Observers should
remember that unlike Yellow-legged Gull which peaks in late summer, Caspian Gull
is predominately an autumn and winter visitor to Britain
4th
Black Duck (54 points, 9/18) For along time this species was declining in
eastern North America due it interbreeding and competition with Mallards. Recently
there has been a resurgence in numbers and this has been mirrored with an increase
in numbers in the South-west. With multiple occurrences in Devon and Cornwall
in recent winters, it only seems a matter of time before one is found here. It
needs someone with patience to sort through thousands of Mallard, to locate what
must be one of the least charismatic birds on the British List.
5th
Isabelline Wheatear (51 points, 11/18) Arriving from its breeding grounds
in Central Asia, Turkey and western Russia in late Sept - early Nov, there have
been 17 records up to 1998, mainly in the east of Britain, but also several on
Scilly or in Wales. The other highly migratory wheatears, Desert, Pied and Black-eared
have occurred here, so it seems only a matter of time before one is discovered,
most likely on a grassy area on one of our coastal headlands.
6th
Cape Verde or Fea's Petrel (46 points, 8/18) Only accepted by the BOU as 'Madeira
/ Cape Verde Petrel' it now seems likely that all observations pertain to the
far commoner Cape Verde, or as it more often called, Fea's Petrel. Most of the
26 records have been in late August and understandably in the south-west, but
a few have occurred in the North Sea. Do these arrive via northern Scotland or
through the Channel? If any take the latter route then the chance of an observation
off say, Portland, must be good, indeed there has already been a sighting of a
Pterodroma sp. there in recent years. The counter argument is that south-western
specialities such as Cory's and Great Shearwaters are commoner in the North Sea
than in Dorset, indicating that the Channel route is not favoured by such seabirds.
7th
Paddyfield Warbler (38 points, 9/18) With over 45 British records this south-western
Russian / central Asian breeder looks overdue for Dorset. This bird might best
be identified in the hand but most recent records in southern Britain have been
in reed beds in the late autumn, a time when little ringing occurs in that habitat.
Away from a permanently manned ringing station (e.g. PBO) the best chance of locating
this bird would be the careful examination of any 'reed warbler' late in the year.
8th
Black-winged Pratincole (31 points, 6/18) There have been 32 records of this
speciality from the steppes of south-west Asia. Like the other two pratincoles
on the British list is highly migratory and as it feeds on the wing often highly
mobile. Unlike the spring arrivals of Collared Pratincole, the Black-winged is
more of a mid-summer to early autumn visitor. A migrating bird could be found
anywhere, but the best chances of twitching one would be if it settled on a wetland
like Lodmoor or Stanpit.
9th
Greater Sand Plover (28 points, 7/18) It was only 21 years ago when the first
was discovered at Pagham. Since then there have been another 11 records. Like
the previous two species it originates from western Asia, a late autumn / winter
arrival date would be likely.
10th
Least Sandpiper (24 points, 4/18) The fourth commonest of the American peeps
in Britain (36 records), the other three (Semi-p Sand, Baird's and White-rumped)
have all occurred in Dorset. Late summer / autumn occurrences are the norm.
11th
Eastern Bonelli's Warbler (21 points, 5/18) The recent splitting of Bonelli's
Warbler has made the identification of this species somewhat tricky, with detailed
vocalisations as well as subtle plumage characteristics needing to be noted. This
a rare bird in world terms with a population of only 1% of that of its western
counterpart. There have been three accepted records so far and few more 'likely
but not provens'.
12th
River Warbler (19 points, 5/18) Many of the 29 records of this east European
and western Asian have been of singing birds in spring. Perhaps one will be discovered
emitting its 'sewing machine' song from an area of dense scrub at Poole Harbour
or at the north end of Radipole one June morning.
13th
Yellow-rumped Warbler (19 points, 4/18) Many correspondents felt the need
to include one Yank passerine in their list, and this proved to be the most popular.
Due to the wholesale destruction of habitat in their Neotropical wintering grounds,
populations of many American migrants have declined sharply in recent years. Yellow-rumps
winter much further north, many within the USA, and may have escaped these depredations.
14th Parrot
Crossbill (18 points, 3/18) Records of this irruptive Fenno-Scandian species,
are understandably clustered in the east, but it has occurred recently in the
New Forest. Clinching a record will need a good view of the bill, something that
seems hard to get on Dorset crossbills! Could occur anywhere, but Wareham Forest
seems the best bet.
15th
King Eider (16 points, 3/18) Once considered only to occur in the far north,
there have been records of females overwintering in Cornwall and a first year
male in Kent in recent years. Careful scrutiny of wintering Common Eiders in Poole
or Portland harbours could pay dividends.
16th
Lanceolated Warbler (15 points, 3/18) Records are increasing as the breeding
range spreads slowly westwards. Fair Isle was always the best site for this skulking
'sibe' but birds have also been seen in East Anglia and as close as Hampshire.
Most records have been of trapped birds, perhaps one will be found in PBO's Heligoland
trap one October morning.
17th
Eurasian Crag-martin (14 points, 4/18) There have been 6 British records,
the earliest was a mere 12 years ago and only one was twitchable. Three of the
records have been on or near the south coast, so Dorset is as likely a venue as
any for this relatively sedentary hirundine.
18th
Black-headed Wagtail (14 points, 3/18) The most distinctive form in the Yellow
Wagtail group, breeding in the Balkans eastwards. It may be some time before it
is given specific status by the BOU, but many birders already consider it 'tickable'.
With only 8 British records it may seem a bit of a long shot, but as interest
in this group continues to grow, unusual wagtails will receive ever greater scrutiny.
19th
Killdeer (13 points, 2/18) With 56 records, this American plover has occurred
in Cornwall, Devon Sussex and Hampshire (including Christchurch Harbour in 1859).
Occurrences typically occur very late in the year following severe trans-Atlantic
storms.
20th
Audouin's Gull (12 points, 2/18) The only species in the top 20 that would
also be a first for Britain (the other, Black-shouldered Kite, appears in the
'also rans'). The population and range of this beautiful gull has increased in
leaps and bounds in recent years and vagrants have occurred as close as northern
France. Perhaps the first British Audouin's will travel north with a group of
Yellow-legged Gulls, so that Holes Bay in late summer could be the place to search.
The
remaining 29 species were:
Canvasback
(9 points, 1/18), Spectacled Warbler (7 points, 3/18), Swinhoe's Storm-petrel
and Solitary Sandpiper (6 points, 1/18), Willet and Black-billed Cuckoo (5 points,
1/18), Blackpoll Warbler (4 points, 3/18), Lesser White-fronted Goose, Lesser
Crested Tern, Sora Rail, White's Thrush and Rose-breasted Grosbeak (4 points,
1/18), Collared Flycatcher and Baltimore Oriole (3 points, 2/18), Greater Yellowlegs
and Siberian Thrush (3 points, 1/18), Grey-cheeked Thrush (2 points, 2/18), Lesser
Kestrel, Baillon's Crake, Slender-billed Gull, Oriental Turtle-dove, Blue-cheeked
Bee-eater, and Crested Lark (2 points, 1/18), Double-crested Cormorant, Black-shouldered
Kite, Western Sandpiper, Long-toed Stint, Cliff Swallow and White-throated Sparrow
(1 points, 1/18).
The
Dorset checklist published by the Club listed 396 species up to the end of 1997.
Since then the 1998 Blyth's Pipits have been accepted and Olivaceous Warbler has
been deleted then re-admitted on the basis of the July 1999 bird. Iberian Chiffchaff
and of course, Marsh Sandpiper are pending, whilst to the best of my knowledge
there has been no documentation of the Chimney Swift in Swanage. Thus the Dorset
list has been increased by one and regrettably seems likely to go through the
magic 400 figure through the process of splitting, rather than by a genuinely
new occurrence.
Ian
Lewis, April 2000.
A summary of Stour Ringing Group's research into the European Nightjar Caprimulgus
europaeus in Dorset. During
1979 whilst setting nets before dawn to ring Sand Martins at a colony near Wareham,
Trevor Squire found it was possible to tape lure and trap European Nightjars (hereafter
Nightjar). Members of the newly formed Stour Ringing Group (SRG) realised that
there was a locally common, yet nationally declining, species about which little
was known of its movements or breeding biology, that could now be ringed with
relative ease. With the permission and co-operation of the Forestry Commission
(now Forest Enterprise) SRG embarked on a study of the species movements and breeding
biology that continues to this day (albeit recently at a much lower intensity).
The work was centred on Wareham Forest, but birds were also studied in Puddletown
Forest and National Nature Reserves adjacent to Poole Harbour and a number of
other sites.
From
1980 until 1983 the emphasis was on trapping adults using a tape lures (Squire
and Alexander 1981) to determine site fidelity, movements between sites and, as
always, in the hope of establishing long distance recoveries. Nests were located
by cold searching by SRG members and also during the routine operations of the
Forestry Commission. Pulli growth rates and development were measured and correlated
with weather and state of the moon. A technique was also developed to safely net
incubating / brooding females on the nest.
Much
of the initiative in this stage was carried out by Ian Alexander and Trevor Squire,
and in 1983 SRG became the first amateur ringing group to use radio-transmitters.
Initial attempts to track nightjars met with limited success, but the radio-tracking
program acquired greater momentum in 1985 when Brian Cresswell joined the group.
Working for Biotrack, his expertise in the construction and fitting of miniature
radio transmitters, and the advent of smaller, more efficient circuits allowed
birds to be tracked over greater distances. Radio transmitters were either glued
to mantle feathers or tied to the retrices. Most were shed within a few weeks;
all were shed by the next moult (Alexander I. and Cresswell B. 1990). Birds were
tracked from a car, both on the network of forestry tracks and on public highways,
on a nightly basis. As it became clear that birds were moving a considerable distance
from their nest sites Dave Eyles was employed (from grants from the Manpower Services
Commission and the World Wildlife Fund) to monitor when in the night tagged birds
returned from foraging to the nest area.
Other
technological innovations included a radio tags with a thermister that was fitted
in the axilla. The lower temperature experienced by the thermistor whilst the
bird was flying, produced a faster signal that discriminated between perched and
active birds. Tiny fluorescent 'beta lights' were attached to the tag allowing
birds to be followed using an image intensifier and this along with the data from
the thermistors identified the 'fly-catching' and 'trawling' feeding methods.
At a later stage, a data logger was positioned close to nests to record the arrivals
and departures of tagged birds by monitoring the signal from their transmitters.
It
is important to emphasise that in spite of this 'hands on' approach there was
no evidence that the birds were harmed or handicapped in any way. Growth rates
from chicks in nest found by radio tracking were identical to those found by routine
forestry operations in areas were adults were neither ringed nor tagged.
A
lot of data was accumulated, most of which has been published, unfortunately the
most important findings occurred a little too late to include in the relevant
volume of BWP. The main discoveries can be summarised under the following headings:
Activity
patterns
Many
trapped birds showed a pronounced 'body bulge', an accumulation of prey items
in the gizzard. Averaging the weight of birds with different sized bulges it was
possible to show that birds could collect up to 10 grams of prey items in foraging
excursions. This bulge was shown to develop quickly in the early evening indicating
that this was the peak feeding time.
Radio
tracking also showed Nightjars to be most active at dusk and dawn and relatively
inactive during the night (Alexander I. and Cresswell B. 1990). A 'trawling' method
of feeding where the bird flew around apparently at random was identified, as
was a 'fly-catching' (strictly 'moth-catching) method, where the bird would sally
out from a perch to catch a specific prey item in the manner of a flycatcher (Cresswell
B. 1996).
Fly-catching
was shown to occur more often during the middle of the night, the birds presumably
having fed by the more rewarding sustained flight after dusk. Fly-catching occurred
more often on warmer and moonlit nights, but then only in the middle part of the
night. Presumably on cooler and darker evenings insect availability was lower
and the more energetic 'trawling' method was required throughout the night. (Cresswell
B. 1990)
Nightjars
feeding away from breeding areas.
Nightjars
have been difficult to study due to their nocturnal habits. It has always been
assumed that birds defend and remain close to a feeding territory. However from
the 1930s to the 1970s a number of papers in Britain and Germany reported birds
feeding away from suitable nesting habitat, sometimes in loose aggregations around
abundant food sources.
Radio
tracking of birds in Dorset showed that Nightjars do not spend all night at their
breeding sites (Alexander I. and Cresswell B. 1990). Most radio-tagged birds left
their roost at dusk and after a short bout of churring (in the case of males),
flew rapidly out of range. Birds were followed by the researchers, initially on
foot, then by car, it often taking several evenings following the same flight
path before the destination of each bird was established. Birds were found to
be feeding at sites up to 7km from the clearings in Wareham Forest; the preferred
habitat was deciduous woodland, orchards, village gardens, ponds, streams and
water meadows. Birds were often found to be using the same area on subsequent
nights and birds that were not radio tagged were occasionally seen in these areas,
although none were ever heard to chur there.
Similar
results were obtained from bird breeding on Hartland Moor NNR with some birds
feeding over salt marsh and other atypical habitats.
The
foraging excursions were often in three distinct phases, an outward flight with
occasional pauses to feed, followed by protracted feeding at the chosen site with
a fast and direct return to the breeding site. Most Nightjars returned from feeding
by the end of the first third of the night and often returned to the feeding area
for a second time before dawn.
Aside
from the SRGs studies, evidence has been accumulating over the past decade that
Nightjars can be observed over the open sea (P. Harris per com). On ten or more
occasions birds have been observed from the Chesil Bank at Ferrybridge flying
low over the sea for protracted periods in a manner resembling that of a storm-petrel
or a Common Sandpiper. The birds have always been seen on still evenings in mid
to late May, but this may be due to observer bias, as these are the times of day
and year when observers visit the Chesil looking for seabird passage. The birds
usually remain a kilometre or more offshore, but have flown close enough on occasions
for a positive identification to be made. It is possible that these birds are
migrants that are 'marking time' until they can come ashore under the cover of
darkness or it is possible that there is sufficient insect life above the sea
surface (presumably blown off the land) for Nightjars to forage.
Evidence
of mate-switching and serial polyandry
From
earlier studies (Lack 1930) it was concluded that Nightjars are double brooded
and that the two nesting attempts overlap. Females would leave the first brood
when about 12 days old in the care of the male and would lay another clutch, by
the time the eggs of the second brood had hatched the first brood had fledged
and both adults could care for the second brood.
Results
of ringing and radio-tagging have indicated that although this may be the case
for many Nightjars this is not the whole picture. Cases of serial polyandry and
mate switching were noted. For example one radio-tagged female left her first
brood to the sole care of her mate - who was also radio-tagged - at about the
predicted time. However instead of starting a new nest nearby she started one
in another clearing 400m away. When she left her new eggs one evening to feed
it was found that they were incubated by another unmarked male. She was never
seen again near her first brood and her first mate was never near her second nest.
She had switched mates.
Although this was the only instance when a female
switching mates was recorded, there were only a few cases where it was known for
certain that a pair had stayed together. It was unusual to find both birds of
a pair radio-tagged throughout the summer, and without tags it was not possible
to identify them at a distance or to recognise birds at a nest site (unless ringed
birds were trapped there). It is all too easy to assume that a bird seen repeatedly
at a particular site is always the same bird. There is often a presumption that
bird pairs show a high level of fidelity, but DNA analysis and studies of marked
birds in a variety of species show that this is not always the case.
Lunar synchronisation of breeding
Another
interesting aspect of Nightjar breeding behaviour is their apparent synchronisation
with the moon (Cresswell B. 1992). Nightjars seem to prefer to start their nests
at the time of the full moon. However, they do so only if the full moon coincides
more or less with the period when they would start nesting anyway. For instance
if a full moon occurs in the first half of June, most nests will be started within
a day or two of it, and there will be relatively few nest start-ups in the week
before and the week after. On the other hand, if the full moon is near the end
of May, just before most Nightjars are ready to start breeding, nest start-ups
will be spread more evenly throughout the first two weeks of June.
It
is difficult to imagine how Nightjars could benefit at the time they start to
synchronise with the lunar cycle. It is likely that the benefits come later instead.
The fledging date of young in a nest that was started on a full moon in early
June would coincide with the next full moon in early July. It is thought that
it is at this time of the 'second' full moon that the Nightjars benefit from their
lunar synchronisation. The extra light provided by the large moon may enable more
efficient foraging, so that adults can satisfy the peak in food demand of their
offspring, and the fledglings will have optimum conditions in which to learn to
forage for themselves.
As
well as being synchronised with moon phase, Nightjar nesting behaviour is also
affected by the weather. In particular cold weather in the period following the
arrival of females from their winter quarters appears to cause them to delay the
date of egg laying (Berry and Bibby 1981).
Nest
and roost sites
The
bare earth 'scrape' that serves as a nest site for this species is usually located
in open areas such as heathland or forestry clearings. However 15% of nests located
by radio-tracking of the adults were located in medium-height plantations more
than 5m high. Nightjars normally lay two eggs but occasionally there is only one.
A nest found by SRG with four eggs comprised of two distinctly marked pairs were
almost certainly from two females.
Mature
plantations rather than clearings, were the preferred roosting sites in 77% of,
mainly male, birds (females usually roosted at the nest site). Nearly 40% roosted
more than 10m above the ground. Other roost sites included fallen branches and
stumps, with only 20% of males roosting on the ground.
These
results are contrary to accepted wisdom and illustrate the problem of observer
bias. Unless a bird can be detected by a method such as radio-tracking then it
will be only found in area where the observer chooses to search for it or are
most likely to find it
Site fidelity
Analysis
of data from birds retrapped in subsequent years revealed that adults remain site
faithful. Of 81 adult birds retrapped, the mean distance moved between years was
0.4km compared to the mean of 4.4km recorded from 44 birds ringed as juveniles
and retrapped in subsequent years. This data was significant for both sexes. (Cresswell
B. 2002) This is not surprising, as adults will presumably return to a location
where they previously bred, whilst juveniles, returning the following year, will
need to find a vacant territory.
Long distance recoveries and causes of mortality.
SRG
have ringed a total of 979 Nightjars of which 28 (2.86%) were subsequently recovered.
Nationwide 84% of Nightjar recoveries are through human related activities such
as collisions with cars, so due to this extreme finding bias, little can be concluded
about causes of mortality. Many of these recoveries occurred close to breeding
areas and hence shed little light on the bird's migration. Similarly the occurrence
of controls (retrapping by ringers other than those who originally ringed the
birds) is highly influenced by the location of specialist ringing groups. Even
so, British ringed Nightjars have been recovered in France (8), Netherlands (1),
Spain (1) and Morocco (2) indicating a migration in a due south direction.
Conservation
It
is clear that the discovery that Nightjars travel considerable distance from their
nest sites to feed has considerable conservation implications, as recognised by
the fact that the species has its own Biodiversity Action Plan. The decline of
the Nightjar from the 1930s to the 1980s (Morris et al) may have as much to do
with the loss of old orchards, hedgerows and watermeadows as it does to the loss
of heathland. Increase use of pesticides may have had an affect of Nightjar numbers,
analogous to that seen in many populations of bats. On the other hand the large
areas of forestry land cleared by felling in has created large areas suitable
for nesting. This however reached its peak the 1980s and many replanted areas
are now no longer suitable, as Nightjars seldom nest in conifer plantation when
they are more than 10 - 20 years old (Morris et al). In Dorset large areas of
former plantation are in the process of being converted back to heathland, however
the work carried out by SRG shows that both breeding and feeding areas must be
conserved.
Further
work
Recent work
has demonstrated that individual churring males may be recognisable through sonogram
analysis, using a dedicated program that analyses both pulse rates and phrase
lengths (Rebbeck, et al 2001). This has major implications for the estimation
of population size and adult survival, however cannot be used to determine how
far an individual bird forages, as they are invariably silent when away from the
nest area.
Acknowledgments
I
wish to thank Brian Cresswell for his constructive comments on earlier versions
of this article.
References
Alexander
I. and Cresswell B. 1990 Foraging of Nightjars Caprimulgus europaeus away from
their nesting areas. Ibis 132 (4): 568 -574
Berry R. and Bibby C. 1981 A breeding
study of Nightjars. British Birds 74: 161-169
Cresswell B. 1990. The effects
of moonlight and temperature on Nightjar foraging. Stour Ringing Group Annual
Report 1989
Cresswell B. 1992 Nightjars and the moon. Stour Ringing Group
Annual Report 1991: 36 - 37.
Cresswell B 1996 Nightjars - some aspects of
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Cresswell
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and Ireland' T&A.D. Poyser
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B. & Stainton, C. (2001) Recognition of individual European nightjars Caprimulgus
europaeus from their song. Ibis, 143, 468-475.
Squire T. and Alexander I.
1981 Capture techniques for full grown Nightjars. Ringers Bull. 5: 132.
Ian Lewis 28/7/03
