IL-MERILL No. 25 1988

ll-MERILL No. 25 1988

lhe coracoids of C. equitum are relatively longer than in other swans (e.q. 74.7mmfor both it and the Larger Bewick 1 S) so its body may have been comparatively b;oader.

THE BREEDING POPULATION OF THE BLUE ROCK THRUSH
MONT/COLA SOL/TAR/US ON COMINO ISLAND IN 1988

Uslits wing-bone Lengths plus the calculated distance between its humeri as wellas formu
based on its WGight, [estimate the feathered wing span of c. equi-tum as
approximately 1.5m. Compared to other swans, its wings were probably more 'eLLiptical'-RAYMOND GALEA & RAYMOND CARUANA

ter 'stoutness' of carpometacarpus and perhaps ulna suggests a higher camber; also,
relatively short hand 'indicates Less attenua7ion than the 1 high-speed' wings 0 -;=, forexample, W'hooper Swans. lhe body and wing shapes I propose for c. equitum and greater

simiLarity of its distal wlng-bone proportions to the more sedentary ~Jl,ute than theWhooper and Bewick's Swans suggest it did not fly far9 However, there is noev dence
support Bate's (1916) assertion, subsequently quoted by other workers. thatC~ equitum had a reduced carpometacarpus and lacked fl lght feathers and was, ther~fore,flightless. lndeed there was no reduction either of 'stoutness' and relative le~ngthsof wine; bones or coracoid or of major flight muscLes, Jts wings were fuLLy feathered aseviden~ed by the presence of fLight feather follicles on ulna and carpometacarpus (Figsand 6.i) and it was light enough to fly.

mic. equitum was abundant and ~t.'idespread on ~rhe island and occurred near both freshand brackish water. lhe goose-Like characters noted above suggest it may have walked weLlon land and, en like other swans, could have taken off and a l i ghted on the ground.

Remai11s of Whooper Swans are found with those of the reLated c. equitum andc. falconeri. l he first occurs at other LeveLs eLsewhere l n Europe but the "two other swans
are found only in IntergLacial deposits of SicuLo/Malta and were evidently endemic, maybe
indigenous. During the ca. 21,COO years of the Interglacial, SlcuLo/Malta was isolated
from the mainland by very strong currents in the Straits of Messina (5ondaar andBoekschoten 1967). On the island, mild climate, plentiful food and Lack of predators( Northcote 198 ·, -83) would have obviated dispersal or escape and encouraged speciation.
Rapid climatic changes terminated the interglacial (Starkel 1977). lhe Less specialised
Whooper Swans migrated; c. falconeri, that had r·educed flight ability (Northcote 1981-83)
and C~ equi~um, perhaps unable to fly far, became extinct.

AcknowledgemenLs
i am gratefuL t0 Mr.~1.j.Ashby who heLped with the ilLustrations and museum curators
who gave me access to their collection~ in particular Dr.G.Zammit-Maempel (NI'vlM) andMessrs.C.A.Walker and G.S .. CowLes

References

Introduction
For the pag 15-20 years, Camino was visited annually in spring, mostly by membersof the Malta Ornithological Society. Records of birds seen were always kept and theBlue Rock lhrush Mon-ticola solitarius was always listed. Estimates of the breeding population were always based on the number of birds seen. Five to ten pairs was the usualestimate. lhe authors of this paper tried to monitor the exact number of Blue Rocklnrushes breeding on the island in 1988.
lne Blue Rock lhrush is a fairly common breeding resident in the Maltese Islands. Itis mainly found breeding along sea cliffs, but some pairs are still to be found inland
alcmg hills, rocky valleys as well as in some fortifications. lhe nest is mostly buiLt
in crags in cliff faces. (Sultana & Gauci 1982).

The Study Arealhe island of Camino separates the main isLands of Malta and Gozo and occupies orly
2.6 sq.km (1 sq.milel. 1he Upper Coralline Limestone rises from the sea to 75 m on thesouth-west side, from where it slopes towards the north-west. It is an exposed andbarren island with little remaining agriculture except in the Santa Marija valley.
Camino has a coastLine of about 9 .. 6 km. (Boffa 1966).

Method and Results
lhe island was visited twice for this census- on 17th and 30 April 1988. Observations were mostly based on singing males. At this time of year females wiLL be in thenest incubating; in fact no females were observed during either visit& A male singing,displaying, or calling the characteristic alarm caLL more than once ln the same area
was counted as a breeding pair. Both visits started early in the morning from Santa
Marija bay, walking very slowly along the cliffs, covering practically the whole of theisland 1 s coastline. Only a few places were not covered as they did not offer sulteble
habitat for the breeding of this species.

1st Visit - 17th April 1988
1916. On a small collection of vertebrate remains from the Gnar Dalam cavern,
with note on a new species of the genus Cygnus. Proc. Zool. Soc. Londs

28421-430.

Brodkorb,P. 1964. Catalogue of fossil birds. Part 2. Anseriformes through Galliformes.
Bull. Fla. St.. Mus. Biol. Sci. 8(3) : 195-335.

lhe first male Blue Rock lhrush was observed singing and flying for shortdistances close to the cliffs about 900m to the east of Santa Marija bay. lhis
bird was also noted flying towards a small chapel in this same bay. lhis chapel
must be a watchpoint marking its territory because it was watched going there
several times, even in past years~
lhe second bird was seen and heard singing twice; once on a small stone hide atll-Hamra and then at a point some distance away from the Redoubt at ll-Miskta.

Howard,H. 1964. Fossil Anserlformes. In: lhe Waterfowl of the World by J.Delacour.
Vol.4 : 233-326. London: Country Life.

2

Lambrecht,K. 1933~ Handbuch der Palaeornithologie. BerLin: Borntraeger.
Northcote,E.M. 1982a~ lhe extinct MaLtese Crane Grus melitensis~ Ibis, 124 : 76·-80.

3

CLose to the Comino lower another singing male was present.
the cemetry walls.

Northcote,E.M. 1982b. Size, form and habit of the extinct Maltese Swan cygnus falconeri.
Ibis, 124 : 148-159.

4At laht il-Mazz a male was observed chasing another male bird, probably the one
seen earlier close to the lower (no: 3). lhis behaviour made it cLear that these
two birds
had overlapping territories and were nesting somewhere along the cliffs
below.

Northcote,E.M. 1981-839 lhe Giant Maltese Swan. Il-Merill
Northcote,E.~1.

1

22 : 6-8.

1984-85. lhe giant fJ1altese Crane. Il-Merill, 23 : 1-4.

Scott,P. and lhe Wildfowl lrust, Slimbridge (eds.). 1972 lhe Swans.
London : Michael Joseph.
Sondaar,P.Y. & Boek.schoten,G.J .. 1967. Quaternary mammals in the South Aegean Island Arc :wlth n0tes on other fossil mammals from the coasral reaions of the Mediterranean. I!.
Proc.

K~Ned. Ak.ad. Wet:. Ser. B, 70 : 565-576.

~1~

Another singing male was later observed perched on an electricity pole at la' Savier.
As this place does not offer ideal breeding habitat for this specie~ it was assumed that
it was one of the males seen chasing each other at laht il-Mazz. Observations ended
at the starting point, i.e. at Santa Marija bay.

2nd Visit - 30th April 1988

StarKel,L. 1977. lhe palaeogeography of mid- and east Europe during the Last cold stage,
with west European comparisons. Phil. Trant~. R. Sec.
Ser. B. (Roy)280 : 351-372.
E., Marjorie Northco~e

It was later seen on

University Departmen~ o;': zoology, Downing Street, Ca.mbr}.. dge,England.

lhis v.isit started at the same time and place as the previous one and the sameroute was taken.
At a point between L'lmnieri and I L-Ponta taL-!1!1erieha, a pair of Blue Rock lhrushes
was uttering alarm calls to each other very frequently and excitedly, on the rocks

IL-MERILL No. 25 1988

IL-MERILL No. 25 1988
below the cliffs6
1his was presumably because of our presence and suggested thatthey had hatched young l11 the nest.
lhis area is fhe same place were we observed

the 1st male on the first visit.
lhe singing male close to the Redoubt in the first visit was again observed in thesame area.
A male bird was observed entering its nesting hole with a smaLl lizard F'odarc::isfilfolensis hanging from its biLL, at 1aht il-Mazz.
lhis suggested +hat this bird

was either feeding its mate or it had young in the nest.
4

lhe other male believed to have its territory over lapplaht il-Mazz, wasn seen hunting inland from laht iobserving the malethat of no:3 atwhile we were still

no:3 with prey in its mouth.

No other birds were seen during this visiL On both visits no Blue Rock lhrushes
were observed on the smaller isLet of Cominotto, although observations were only n1adefrom Camino. After these two visits it was concluded that the breeding population ofthe BLue Rock lhrush on the island of Camino was mace up of four pairs.

---------·N

A typical nesting-site of the Blue Rock Thrush on Camino Island, with loose rocks beneaththe cliffs. (Photo : Raymond Caruana)
It is also a fact that stealing of young from the pairs at laht il-Mazz takes place
every year. lhis might also have an effect on the breeding population of this bird on theisland,

Summary
A census of Blue Rock lhrushes breeding on the island of Camino in April 1988
located 4 singing males, observed during two visits by the authors. No birds were foundbreeding inland.
Inland nesting is practically impossible as all ruins and otherbuildings on the island are all subject to human predation and disturbance. All birds
observed were breeding in almost inaccessible parts of the cliffs. It is also to be
nored that the four pairs located all chose a habitat with loose rocks beneath thenesting-site.

Acknowledgement
We are grateful to Charles Gauc i for h l s comments and also for correcting this paper.

References-_j~_

Map of Camino showing breeding areas of 4 Blue Rock Thrush pairs in Spring 1988.
Numbers 1 to 4 (circled) refer to numbers in the text. Names of places mentioned in
the text are all marked on the map.
Conclusion
SimiLar exercises in the future wiLL show if the population of the Blue Hock lhrush
on Camino is a stable one or ~ot. 1f the popuLation will remain the same for several years
it can be assumed that this i Land can only hold four pairs.
lhere are many suitablenesting places where these bir scan nest but the feeding areas on top of the island play
an important part in the terr tory of such species.

Sultana,J. & Gauci,C. 1982 A New Guide to the Birds of r~alta. 1he Ornithological Society:
Valletta, Malta.
Boffa,C.J. 1966 1he Islets of Camino and Fi lfla. Lux Press, Malta ..

Raymond Galea- 'Osprey', Ganu Street, B'Kara, Malta.
Raymond Caruana- 'Flamingo', Triq il-Huttafa, Fgura, Malta.

IL-MERILL No. 25 1988

IL-MERILL No. 25 1988
below the cliffs6
1his was presumably because of our presence and suggested thatthey had hatched young l11 the nest.
lhis area is fhe same place were we observed

the 1st male on the first visit.
lhe singing male close to the Redoubt in the first visit was again observed in thesame area.
A male bird was observed entering its nesting hole with a smaLl lizard F'odarc::isfilfolensis hanging from its biLL, at 1aht il-Mazz.
lhis suggested +hat this bird

was either feeding its mate or it had young in the nest.
4

lhe other male believed to have its territory over lapplaht il-Mazz, wasn seen hunting inland from laht iobserving the malethat of no:3 atwhile we were still

no:3 with prey in its mouth.

No other birds were seen during this visiL On both visits no Blue Rock lhrushes
were observed on the smaller isLet of Cominotto, although observations were only n1adefrom Camino. After these two visits it was concluded that the breeding population ofthe BLue Rock lhrush on the island of Camino was mace up of four pairs.

---------·N

A typical nesting-site of the Blue Rock Thrush on Camino Island, with loose rocks beneaththe cliffs. (Photo : Raymond Caruana)
It is also a fact that stealing of young from the pairs at laht il-Mazz takes place
every year. lhis might also have an effect on the breeding population of this bird on theisland,

Summary
A census of Blue Rock lhrushes breeding on the island of Camino in April 1988
located 4 singing males, observed during two visits by the authors. No birds were foundbreeding inland.
Inland nesting is practically impossible as all ruins and otherbuildings on the island are all subject to human predation and disturbance. All birds
observed were breeding in almost inaccessible parts of the cliffs. It is also to be
nored that the four pairs located all chose a habitat with loose rocks beneath thenesting-site.

Acknowledgement
We are grateful to Charles Gauc i for h l s comments and also for correcting this paper.

References-_j~_

Map of Camino showing breeding areas of 4 Blue Rock Thrush pairs in Spring 1988.
Numbers 1 to 4 (circled) refer to numbers in the text. Names of places mentioned in
the text are all marked on the map.
Conclusion
SimiLar exercises in the future wiLL show if the population of the Blue Hock lhrush
on Camino is a stable one or ~ot. 1f the popuLation will remain the same for several years
it can be assumed that this i Land can only hold four pairs.
lhere are many suitablenesting places where these bir scan nest but the feeding areas on top of the island play
an important part in the terr tory of such species.

Sultana,J. & Gauci,C. 1982 A New Guide to the Birds of r~alta. 1he Ornithological Society:
Valletta, Malta.
Boffa,C.J. 1966 1he Islets of Camino and Fi lfla. Lux Press, Malta ..

Raymond Galea- 'Osprey', Ganu Street, B'Kara, Malta.
Raymond Caruana- 'Flamingo', Triq il-Huttafa, Fgura, Malta.