Breeding Biology of the Sand Martin or Bank Swallow (Riparia riparia)
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| License | CC Attribution - NonCommercial - NoDerivatives 3.0 Germany: You are free to use, copy, distribute and transmit the work or content in unchanged form for any legal and non-commercial purpose as long as the work is attributed to the author in the manner specified by the author or licensor. | |
| Identifiers | 10.3203/IWF/D-1569eng (DOI) | |
| IWF Signature | D 1569 | |
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| Production Year | 1981 |
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| IWF Technical Data | Film, 16 mm, LT, 194 m ; F, 18 min |
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Transcript: English(auto-generated)
00:01
Breeding biology of the sand marten. Gravel pits with steep sandy walls have become the most important nesting biotope for sand martens in central Europe.
00:22
They have superseded sandy river banks which have almost disappeared from the cultivated landscape. Sand martens are the smallest European representatives of the swallow family. Their tawny dorsal and white ventral plumage and their brownish breast band distinguish them from the house martens
00:40
and swallows. Like these they are migrants to Europe in spring and summer. They hatch their young in self excavated burrows from 50 centimeters to one meter in length. The same section of embankment at the beginning of colonization in early May. An individual is starting to
01:03
excavate a nesting burrow. At first every little projection in the sand wall is utilized. With scratching movements of one foot, in this case the left one, the bird makes the first depression.
01:21
Its right wing is outspread to help it maintain balance. Hovering in front of the bank it sometimes uses both feet simultaneously in digging. As long as the birds are still observable while burrowing they are very wary. They flee at the slightest propagation.
01:49
Coarse-grained largely clayless layers of sand erode more rapidly than those containing large amounts of clay. This gives rise to ledges which provide the birds with footholds. Coarse-grained deposits are also
02:02
easier to excavate. They are preferred sites for burrowing. The burrows are excavated almost exclusively by males. They cannot be distinguished externally from the females but they each have a sex specific call. The male's call consists of a rapid
02:24
sequence of short notes. Loose sand is scraped out after the bird alights. To excavate the tunnel and the broader and deeper nesting chamber
02:43
a male may take anything from one to ten days, the average being four days. The burrows often lie side by side following the softer strata. Usually less than half of them are occupied since many birds attempt several burrows. Favourable burrowing sites are often the scene of rivalry displays because many birds will be digging simultaneously. These two
03:05
are excavating very close to one another. The marten on the left calls against the right hand one and this bird in turn threatens a third. The one
03:21
on the right at first continues to excavate but then flies off. Calls accompanied by raised head plumage deter it from landing again. An intruding marten attempts to invade an occupied burrow.
03:43
The occupier prevents it and pursues it as it flees. Male and female birds often cooperate in defending their burrows. The cork in the tunnel entrance joins the hen in warning off the intruder to the right.
04:02
If an intruder cannot be deterred a fight may ensue. Because of this tunnel defence behaviour the distance between simultaneously excavated entrances is about 50 centimetres. Later arrivals dig their tunnels in the intervening spaces.
04:22
Mating takes place either before, during or on completion of tunnel building. Not much is known about actual mating procedures. The same female can be observed to visit an excavating male repeatedly. She often refuses to fly off even when initially attacked.
05:05
The call of the female. The various calls
05:21
of the San Martins were not recorded in synchrony with the film but have been dubbed onto the appropriate shots. Alternating calls
05:43
and occasional preening of the partner's plumage are probably behaviours that accompany partner bonding. Once the burrow is ready and mating has taken place both partners start collecting nesting materials.
06:03
They independently fly out in search of dry grass and roots carrying these back to the nesting chamber. Nest building takes two to three days.
06:27
The approach flight in slight slow motion. Some birds steal nesting material from unguarded burrows.
06:40
Once the nest is complete, cork and hen remain together all the time. They sit together in the nesting chamber or at the tunnel mouth and fly out in company too. The pair flight phase lasts about seven days.
07:02
Occasionally the pair will alight on telegraph wires and copulate. About the fourth day the female begins to lay. One egg is produced each day until the standard clutch of five eggs is attained. When the last egg but one has been laid the birds begin to incubate.
07:24
The partners take this in turns. On the right a male is excavating a new burrow. The incubating neighbours usually leave him in peace. He defends his burrow vigorously against rivals.
08:04
Throughout the brooding period the nest is lined with feathers. The colony is fairly quiet during the main period of incubating activity. The non-brooding partners are off in search of food or feathers. Occasionally a whole swarm of martins will hover about in front of the embankment.
08:24
They utter warning calls. This mobbing can be observed when a competitor such as a sparrow is detected in the sand pit or a predator approaches the colony.
08:46
The first young hatch after 15 days. The empty shells are removed from the nesting chamber. The partners take turns at brooding the young. While one parent remains with the offspring the other is hunting insects on the wing.
09:01
They feed the chicks five to eight times an hour. After the first week both parents go foraging at the same time. Now they remove the droppings of their brood. The young remain in the nesting chamber or tunnel for a good two and a half weeks.
09:24
Only then do they emerge into daylight for a while and perch at the tunnel entrance for increasing periods of time. They observe their surroundings alertly. They show great tolerance among themselves.
09:43
There appears to be no sort of hierarchy at all. If danger threatens or a warning call is heard they immediately disappear inside the nesting tunnel. The young are fed more frequently now.
10:14
One or two chicks are looked after at each feeding. The satisfied ones stop begging. In this way the food is distributed fairly among all the siblings.
10:27
Luring is practiced by the parents. Here one of the adults is calling at the tunnel entrance. All the young assemble there and perch facing it. The young also vocalize.
10:50
After taking off the parent bird remains in the vicinity and maintains vocal contact with the young.
11:05
Vocal contact between adult and offspring is an important factor in establishing family cohesion after fledging of the chicks. On the 20th to 24th day they fly out for the first time.
11:22
The parent lures the fledgling with calls and it follows. After a short flight both return to the nest. Renewed luring.
11:42
Parent and juvenile calls of the San Martin each have signature characters. Discrimination tests with playbacks prove that parents and young recognize each other by such calls. Neutral recognition is very important during these early flights. It enables the young to find their way back to the burrow even before they are capable of finding it on their own.
12:02
For instance if they have approached a foreign burrow by mistake or after falling out of the burrow. This sometimes happens when a fledgling leans too far out of the burrow entrance in an attempt to defecate.
12:27
Fallen fledglings seek cover or cower. They utter occasional calls which help the parents to locate them.
12:43
The young follows the luring of the adult. When all the young are fully fledged the whole family goes out on foraging expeditions near the colony.
13:01
The families maintain their distance even when neighbors are within easy reach. Intruders are attacked by both parents and offspring. Although the young stranger is begging the adult drives it off. The young intruder on the far left
13:22
is pecked by the occupant. It loses the foothold lands again and is threatened.
13:55
As the siblings of one family live in harmony but attack alien birds they must be able to recognize each other.
14:03
They too can distinguish between sibling calls and strangers calls. The alien fledgling is evicted by the adult.
14:28
Between the 25th and 30th days the young become independent of their parents and flock with juveniles that may even originate from neighboring colonies.
14:46
From time to time they invade a particular colony. Like adults excavating burrows they scratch and dig at the sand walls
15:00
but their attempts at tunnel building rarely progress more than a few centimeters deep. The significance of this tunnel building behavior immediately after the young have achieved independence is as yet unexplained.
15:23
The scouting behavior of the juvenile flocks in the rearing grounds before their migration to Africa is doubtless of great importance to the sand martin enabling it to recognize the nesting grounds on its return the following year. More than half of the adult birds raise two families a year in the same colony.
15:42
Males and females generally take new mates. It sometimes happens that a female mates again while her first partner is still attending to the first brood. The male either enlarges the old tunnel or like this martin excavates a new one.
16:20
Disused burrows are reoccupied and the old nests thrown out during renovation. The nesting tunnels are actively defended against rivals just as they were before the first brood.
16:42
The second nesting cycle follows in exactly the same way as the first. Erosion will have obliterated or closed up most of the tunnels next year. Many of the sand martins will return to the colony and nest here again if the conditions in the gravel pit are still favorable.