on starlings (Sturnus vulgaris) in England

ento.org.nz

on starlings (Sturnus vulgaris) in England

The seasonal incidence of parasitism by Phthiraptera

on starlings (Sturnus vulgaris) in England

P. R. KETTLE*

King's College (University of London), Strand, London WC2R 2LS, England

Abstract

The seasonal prevalence of chewing lice (Phthiraptera) on starlings (Sturnus uukaris)

from Hampshire and Sussex was monitored for one year. Four species of lice were

recovered: the menoponids Menacanthus eurysternus and Myrsidea cucullaris, and the

philopterids Brueelia nebulosa and Sturnidoecus sturni. Birds most frequently harboured

populations of fewer than 10 lice. Juvenile birds were particularly lousy and their louse

populations showed a dramatic decline associated with moulting. Menoponids were

most prevalent in August and September and philopterids in June and July. From the

data obtained, it appears that the chief factors which govern the size of louse

populations are host behaviour (preening), moulting, and climate.

Keywords: Phthiraptera; Menoponidae; Philopteridae; Aves; Sturnus vulgaris;

preening; parasitism; England.

INTRODUCTION

Avian lice show a general tendency to be most numerous during or immediaely prior

to the host's breeding season - early spring. This pattern has been recorded by Ash

(1960) on numerous British passerines, by Boyd (1951) on starlings (Sturnus uulpris L.)

in the U.S.A., by Baum (1968) on blackbird (Turdu~ merula L.) in Germany, by

Woodman & Dicke (1954) on house sparrows (Passer domesticus L.) in the U.S.A., and

by Foster (1969) on orange-crowned warblers (Vermiuora celata (Say)) also in the U.S.A.

The only known findings differing significantly from those above are for populations

on bobwhite quail (Colinus virginianus L.) in Southern Illinois. In this case Bergstrand &

Klimstra (1964) found parasite populations to be lowest in January and February and

highest in late summer.

In order to study the seasonal distribution of avian Mallophaga, factors affecting

them, and geographic variability, a year-long survey was undertaken. Starlings were

chosen as the most suitable host species because: (i) they are not protected by law and

are regarded as being pests; (ii) they harbour 2 menoponids - Menacanthus eurysternus

(Burmeister, 1838) sens. lat. and Myrsidea cucullaris (Nitzsch, 1818), and 2 philop-

terids - Brueelia nebulosa (Burmeister, 1838) and Sturnidoecus sturni (Schrank, 1776);

*Author's present addrrss: Wallaceville Animal Research Centrr, Ministry of Agiculturr and Fishcrirs,

Private Bag, Upper Hutt, Nrw Zraland.


404 New Zealand Entomologist, 1983, Vol. 7, No. 4

(iii) findings could be compared with those of Boyd (1951) and Touleshkov (1965)

from the U.S.A. and Bulgaria, respectively.

MATERIALS AND METHODS

Time available coupled with the difficulty of securing birds during the summer

months necessitated the selection of a small sample size. Ten were collected each

month, but analysis was carried out on 2 monthly samples - giving an adequate

sample size of 20.

All birds were collected within a 32 km radius of Petersfield, Hampshire (51°N,

0°56'W). Birds were either shot (October, and April-September inclusive) or mist-

netted (November-March).

Lice were removed from dead birds by first fumigating them with chloroform in a

plastic bag, then by washing with detergent-charged water. Each bird was given a

standardised wash involving 3 changes of water and all washings were passed through a

BS 80 mesh sieve (0.2 mm) to gather the lice. Live birds were deloused using the "Dri-

Die" method of Kettle (1975). [Marketed in New Zealand by Associated Rural

Industries Ltd., Box 13-083, Onehunga; consists of pyrethrin 1.00, technical piperonyl

butoxide 10.00, amorphous silica gel 40.00, petroleum base oil 49.00 by weight]. This

involved dusting the birds thoroughly with "Dri-Die" (a combined desiccant and

insecticide) then leaving them in a cage for a minimum of 30 minutes after which time

they were released. All birds were weighed and their sex determined (except in the case

of juveniles) whether they were captured and released or were shot. The efficacy of the

"Dri-Die" delousing technique was determined by first delousing a sample of 10 birds

with "Dri-Die" then washing them in the standard manner outlined abbve. From the

10 birds 156 lice were recovered - 117 by dusting and 39 by washing. Not all species

were equally represented in the collection (Brueelia dominated with 133 specimens) so a

common correction factor was calculated to apply to all "Dri-Die" results. Seventy-

five percent of the population, as estimated by combined "Dri-Die" and washing, was

recovered by the "Dri-Die" technique and from the figures obtained for Brueelia it

appears that the percentage recovered was similar fir all stages (Brueelia stages

recovered, "Dri-Die" figures first followed by washing figures 16, 2: I1 9, 5: I11 13, 2:

36, 4; 9 31, 11). Accordingly, "Dri-Die" recoveries were multiplied by a

correction factor of 1.33 before the ;instruction of Figs 1-4. Actual recoveries (washed)

are plotted for October and for April to September inclusive. To calculate actual

("Dri-Die") recoveries of lice for November to March inclusive points in the Figs may

be multiplikd by 0.75. The overall pattern remains basically the same whether

corrected or actual recoveries are plotted.

Lice were mounted in gum chloral and the species composition of populations

determined. Instars were identifiable by temple breadth, measured by use of an

eyepiece micrometer (Table 1).

Table 1. Head breadth at temples (in mm).

Brueelza Sturnidoectlr Menacanthur My~sidea


New Zealand Entomologist, 1983, Vol. 7, No. 4

1

Months

3 Months

Figs 1-4. Seasonal density and age structure of 4 louse species recovered from starlings (Sturnus uukaris): 1,

Brueelia nebulosa; 2, Sturnidoecus sturni, 3, Menacanthus eurysternus; 4, Myrsidea cucullaris.

* = mean number of lice on adult birds.

I I

Figs 5-6. The seasonal incidence of parasitism by lice occurring on starlings: 5, Menoponidae -

Menacanthus eurysternus and Myrsidea cucullaris; 6, Philopteridae - Brueelia nebulosa and Sturnidoecus sturni.

RESULTS

The seasonal distribution of the 4 species of lice is given in Figs 1-4. Seasonal

incidence is shown in Figs 5 and 6.

Of the total sample of 118 birds 4 individuals had louse populations exceeding 100.

All of these birds were juveniles. The individual with the largest number of lice was

collected in June and harboured 247 (Brueelia, 178: Sturnidoecus, 51; Menacanthus, 6;

Myrsidea, 12). The highest numbers of individuals of a species recorded from single

2

Months

Months

d -:

0 ', , , , , , , , , , ,

O N D J F M A M J J A S O N D J F M A M J J A ,

5 Months 6 Months


406 New Zealand Entomologist, 1983, Vol. 7, No. 4

hosts were: Brueelia, 178 (June); Sturnidoecus, 125 (July); Menacanthus, 75 (September);

and Myrsidea, 94 (September).

The sample was heavily biased in favour of male birds but no difference in louse

populations attributable to the sex of the host was detected. There was no significant

difference in louse burden between light and heavy birds (t = 0.78 when comparing

most lousy 10 and least lousy 10 birds in April and May) when adults alone were

considered. However, juveniles were significantly more lousy than adults during June,

July, and September (Table 4).

DISCUSSION

The weather conditions during the year of this survey were atypical for the region

from which the birds were collected. Within the trial period - October 1975 to

September 1976 - there was a mild winter, an early spring, and a hot dry summer.

A most noticeable feature of Figs 1-4 is that they do not conform to a single pattern.

Broadly the philopterids, Brueelia and Sturnidoecus, show a similar pattern of incidence

with populations being relatively low from late summer through mid winter, then

building up to an early summer peak on adult hosts with absolute populations being

greatest during June and July when juveniles are particularly heavily parasitised.

Sturnidoecus differs from Brueelia in having an earlier population peak on adults and in

having higher winter numbers. The reasons for the population crash between

FebruaryJMarch and AprilJMay are unknown but could be a combination of factors.

Sturnidoecus is found on the host's head and perhaps mutual preening by pairs of

starling reduces louse numbers. It may also be that the lice transfer to nestlings at an

early age so that while the figures indicate a marked decline of lice they may be present

in higher numbers on birds outside the range of sampling.

The menoponids show population patterns similar to one another but they too are

out of phase. There is some evidence suggesting a progressive build up of the

population of Menacanthus as the host's breeding season progresses (from April

onwards) but this did not occur with Myrsidea.

Nymphs were present in the louse population throughout the year with the exception

of Brueelia which was not obtained in October and November. This lack of Brueelia

nymphs is probably a reflection of the sample size rather than the true situation.

Moulting took place between July and August and appears to have been the key

factor in reducing the philopterid populations but there is no indication that the

menoponids were affected.

Birds most frequently harboured louse populations of fewer than 11 (Table 3). The

most common combination of species was Brueelia, Sturnidoecus, and Myrsidea (Table 2).

No birds were found to harbour populations consisting only of Sturnidoecus and

Menacanthus but these lice were found together on the same host when another species

was also present. The combinations on individual hosts of either Brueelia plus

Sturnidoecus or all 4 species were equally common (Table 2).

Juvenile birds were found to be particularly lousy and their louse population showed

a very marked decline associated with moulting (July and August). This decline in

louse populations at moulting was not apparent in adult birds (Table 4).

Boyd (1951) in her survey of starling parasites in the U.S.A. recorded the incidence

of lice but did not examine the population structure. Her figures do not correlate with

those given here. She found that the incidence of both Bruellia and Menacanthus was

lowest in January. This may be related to the more severe North American winter but

other factors could be involved. Of particular interest was the fact that she recorded

only Brueelia and Menacanthus from the 300 birds she examined. Starlings were

introduced into the U.S.A. from Europe in 1890 and 1891 when a total of 100 were

released in New York (Austin 1962) and it appears that only 2 of their "normal" 4

species of lice have become established.


New Zealand Entomologist, 1983, Vol. 7, No. 4

Table 2. Frequency of parasite combinations on individual hosts (1 = Bruelia, 2 = Sturnidoecur, 3 =

Myrsidea, 4 = Menacanthus).

No. of birds

Brueelia only 9

Sturnidoecus only 3

Myrsidm only 6

Menacanthur only 9

(1) (2) (3) (4) 14

(1) (2) 14

(1 (3) 1

(1) (4) 2

Table 3. Frequency distribution of lice on individual birds.

Number of lice

0 1-10 11-25 26-50 51-100 101 +

Brueelia 44 46 18 7 2 1

Sturnidoecus 50 44 15 5 3 1

Menacanthus 79 29 7 3 1 0

Myrsidea 50 52 13 2 1 0

All lice 11 44 32 18 9 4

Table 4. Comparison of louse burdens on juvenile and adult hosts. The mean number of licelbird is given,

followed by total number of birds in parentheses.

1976 Juveniles Adults

June

July

August

September

The present findings are broadly comparable with those of Touleshkov (1965) who

examined starlings in Bulgaria. The same combinations of species on individual host

were shown to be common, moulting was found to reduce louse populations greatly,

and the louse burdens did not show variation associated with the sex of the host.

Starling lice show no evidence of being influenced by hormones produced by the host

as has been suggested by Foster (1969) to be the case for lice on orange crowned

warblers (Vermiuora celata). Populations are probably mainly controlled by the host's

preening activities but the moult is a major factor in reducing philopterid populations.

It appears likely that once juveniles have moulted and learnt to forage efficiently, their

preening ability, or perhaps time involved in preening, increases so that by winter a

balance is reached between host and parasite. There is evidence (Boyd 1951) which

suggests that weather conditions may also play a modifying role on the hostlparasite

relationship so that one may summarise the factors influencing louse populations in

possible order of importance as (i) host's activities, expecially preening; (ii) moulting;

and (iii) climate. These factors are, however, interdependent as for normal preening

behaviour and moulting adequate food must be available and this is dependent on

climate.

Although this work was carried out in England, the results are presented here with a

view to encouraging a comparable study in New Zealand. In New Zealand the starling

is a common introduced bird of some economic importance and is apparently

parasitised by 3 of the 4 species of lice recorded in this study. To date M. cucullaris has

not been reported in New Zealand.

407


408 New Zealand Entomologist, 1983, Vol. 7, No. 4

ACKNOWLEDGMENTS

I wish to thank Mr A. W. Barkus for preparing the figures.

REFERENCES

ASH, J. S. 1960: A study of the Mallophaga of birds with particular rcfrrrncr to their ecology. Ibis

102:93-110.

AUSTIN, 0 . L. JR. 1962: Birds of the World. London, Hamlyn. 317 p.

BAUM, H. 1968: Biologie und Okologie der Amselfederl a use. Anxewandte paraitolo,

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