West Midland Bird Club

'Some Breeding-habits Of Marsh-Warblers In South Worcestershire', 1938

This article, by a then-prominent member of the Club, first appeared in ‘British Birds’ issue 32:7 (pages 230–232), in December 1938. 

Bird and place names were spelt as shown. For their current status, please see our county lists.

Some breeding-habits of Marsh-Warblers in South Worcestershire.
A. J. Harthan.

Marsh-Warblers (Acrocephalus palustris) are local but not uncommon in the lower Avon valley where they nest chiefly in osier beds and similar moist places. I had not found any breeding away from such haunts until 1938, when five pairs nested in a bean-field one mile distant and 200 feet above the river valley. All ditch and pond water near this field had dried up before their arrival during an unusual drought which lasted from early February. until the end of June. Since five pairs arrived in the same field, a new breeding haunt, a few observations I made whilst they nested in such dry surroundings may be of some interest.

May 30th to June 6th: A single cock sang in a tall hedge adjoining the bean-field and another arrived on June 7th. I stuck several sticks up in the beans hoping that they might be used as song perches and that subsequently nests would be built near them. None were ever used for this purpose. Four nests were close to an open furrow between lands where oats, seeded from last years crop, formed thin but distinct guidelines through the uniform mat of beans.

June 8th to 12th: Both cocks were chasing hens in short pursuit flights to and from the hedge. Here they sang vigorously, slowly advancing towards each other until they met in the lower branches of a crab tree which was the boundary of their territories. They flitted about the twigs of this neutral ground until one would dart along the hedge in search of a hen closely pursued by the other. After much twisting and chasing these bickering flights ended with both cocks facing each other with lowered heads turning from side to side, throats puffed out and wings quivering in hurried, angry spasms of song. I saw no "beak and claw" combats. Meanwhile the hens continued feeding or resting and ignored the cocks' violent behaviour, but they were instantly chased by them, if they left the hedge.

Nest building began on June 12th and each pair kept within its own territory. Three Marsh-Warbler nests near the river contained 2, 2 and 5 eggs respectively on the same date. The hen did most of the nest building, collecting all the material within an area 8 yards long in the hedge bottom whilst the cock flitted about just above her, frequently singing and hastily plucked whatever was to hand when she flew to the nest. The contrast between the considerable, trailing wad of material in her bill and the few token grass stems carried by the cock was always most evident. All sizes of dead grass stems, with and without leaf blades and sometimes with roots attached, were used to build a hammock-like foundation upon six to ten long stalks slung between two bean stems. A few beakfuls of sheeps wool were stuck about the outside of the nest whose interior was lined with fine grasses, roots and horsehair (actually white tail hairs from Hereford bullocks, collected off a barb-wire fence next the hedge). All five nests were alike in construction and size but varied greatly in the amount of horsehair lining. Exterior dimensions: 4½ inches across “handles”, 3 inches the other way, tapering to 2 inches across the bottom which was 4 inches below the rim of the nest. Interior dimensions 1¾ inches diameter by 1¾ inches deep. The nests were about 18 inches above ground and 9 below top of bean stems and were poorly concealed by leaves until a burst of growth towards end of June.

June 15th: Two nests were lined and two more cocks arrived. One usurped territory from the first pair where an ash sapling formed a boundary mark, the other spent a harassed day flying about the hedge in search of some part where he might sing undisturbed, gradually moving down the field until he was attacked by a pair of Whitethroats feeding young. He finally established himself close to a fifth pair of Marsh-Warblers that had occupied the highest point in the middle of the field since June 12th. Three nests were built about 50 yards apart close to the hedge and two far away in the centre of the beans.

The first two clutches were laid between June 17th and 21st, and four eggs were laid in each of the five nests. Brooding birds slipped silently and almost invisibly into the surrounding herbage when flushed, but one of them, possibly a cock, frequently gave a short burst of Sedge-Warbler-like chatter. Song ceased abruptly when incubation began. On June 26th a gale turned one nest over so that the eggs were brooded on its rim in a most precarious manner. I righted it by placing a supporting twig beneath but the eggs were immediately taken by a Magpie that was chattering in the hedge whilst I adjusted this nest. Little Owls were feeding two lots of young in hollow crab trees close to the Marsh-Warblers' nests but the only bird remains that I found there were young Blackbirds, Thrushes and Whitethroats. The first Marsh-Warbler nestlings flew on July 13th. Both adults now made a loud “pebbly” churring as well as the usual “tic-cheruk” alarm note, and the cock gave short bursts of song which included Redstart alarm notes. I saw four separate broods of Marsh-Warblers in the field on July 26th. They were easily distinguished from the innumerable young Whitethroats, Garden-Warblers and Yellow Buntings [1] feeding on bean aphis, by their distinctive churring. I heard frequent, but feeble, snatches of song from July 18th to 26th, and one cock sang with pre-nesting vigour throughout the morning of July 19th. All had left the field by August 2nd.

Song consisted of the usual mimicry connected by a subdued Sedge-Warbler-like gabble and was frequently interrupted by a loud whistle of fast, rippling notes. Of mimicry I heard the following:

[1^] The Yellow Bunting is now known as the Yellowhammer.

Reproduced by kind permission of British Birds *.
Thanks to Dr. Malcolm Ogilvie for scanning the original, from his collection.

© West Midland Bird Club, 147 World's End Lane, Birmingham, England B32 1JX
Registered charity, number 213311

Ornithology in Staffordshire, Warwickshire, Worcestershire & the West Midlands county, since 1929.

Fetched from http://www.westmidlandbirdclub.com/bibliography/british-birds/32-230.htm on Wednesday 16 April 2014 11:53:18

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