What motivates the food bringing behaviour of the peregrine falcon throughout breeding?

247

Behavioural Processes, 33 (1995) 247-256 0 1995 Elsevier Science B.V. All rights reserved 0376-6357/95/$09.50

BEPROC 00562

What motivates the food bringing behaviour of the peregrine falcon throughout breeding? P. Carlier * and A. Callo Centre de Recherche

en Biologic

du comportement

(Accepted

(URA CNRS 664),

Toulouse,

France

2 May 1994)

Abstract

Wild

peregrine

courtship

put forward breeding motivation

underlying

the motivation

the food

bringing

easier with

during

incubation

what

feed the offspring.

Until

on the females’

control:

behaviour

male - linked

to reversed

duty schedule

since it prevents

Key words:

Peregrine

of the male

* Corresponding author. SSDl 0376-6357(94)00027-E

(i) During

interactions,

the the

courtship,

the

may learn to bring prey

of incubation,

if the males

than if they beg for a brooding

stage, the possibility of male - female peregrine.

the occurrence

Falco peregrinus

Male

and

throughout

turn.

may be to incubate.

(iii)

from males and females are performed

sexual size dimorphism

falcon;

Food transfer;

from

behaviour

of a male reaching

to

the young

males transfer food to females in order to give food to the

This study stresses the influence

of the parental

observed

and to the sex involved,

males’ food bringing

the food bringing

the fledgling

period

(ii> In the course

motivates

been

this behaviour

is different.

in landed

the mate.

have

of the food bringing

underlying

behaviour

by the females

As soon as the eggs are pipped, depends

brook&)

food transfers they are more likely to incubate

Therefore,

young.

peregrinus

to the stage of the breeding

dominated

the contact

(Falco

about

According

males, physically perform

pairs

stage. We analyse the typology

explanations

period.

to make

falcon

until fledgling

- female

relationships

The dominance - should

of conflicts

brook&;

relationships;

upon the expression

of the female

over the

be necessary to ‘manage’ harmful

Parental

behaviour;

Reversed

the

to the offspring.

Food bringing;

sexual size dimorphism

248

Cade (1960)

emphasized

the performance

of giving prey to its mate in the peregrine

falcon. This falcon is very possessive with food and many interactions outside the breeding period are agonistic and concern food acquisition. Many studies have stressed the function of courtship feeding on formation Willoughby

and Cade,

mons, 1980;

1964;

Ratcliffe, 1980;

and reinforcement

Nelson, Monneret,

1970;

Wrege

1987).

of pair bonds (e.g. Cade, and Cade,

1977;

1960;

Cramp and Sim-

It is worth noting that the peregrine falcon

is usually faithful to its site and to its mate as long as this one is alive. Like Lack (1940), subsequent

feeding

Cade (1960)

connected

of the female

male’s food bringing behaviour

during

courtship feeding with copulation

incubation.

Monneret

and

redirected

outside

the eyrie,

including the male. This one, being dominated, predation,

that

the female’s aggressive-

is toward

her environment

redirects his own aggressiveness toward

quelling the female by mean of prey offering.

The behavioural

pattern of food bringing, and especially the prey transfer, has been

studied

by Cade

(1960)

(1983),

Monneret

(1987),

(1977)

and the

regarding the

during the nestling stage, suggested that newly hatched

young mean an intrusion at the centre of territory. Consequently, ness is stimulated

(1974),

Nelson

(1970),

Carlier (1992)

Treleaven

(1977)

Sherrod

(1982),

Hustler

in wild peregrine pairs, and by Wrege and Cade

in captive pairs.

The aim of this study is to analyse the typology of food bringing behaviour modifications

throughout

and its

the breeding period, and to put forward suggestions about the

different motivations likely to underly the food bringing behaviour.

‘aterial and Methods The observations extended west of Massif Central, February

to March

1988

February to June 1989

over two breeding seasons in the region of Quercy (south

France): (I)

from February to June 1988 for 2 nesting sites, from

for 1 site, the three totalling

26 observation-days,

for 5 sites, and from February to March

totalling 66 observation-days.

1989

(2)

from

for 1 site, the six

The site included the nest and the area around it that the

pair actually occupied. The finely quantified observations usually lasted at Least 3 consecutive hours and totalled 720 hours. The sites were chosen on a criterion of visibility inside the eyrie, two were lost in the course of study because of the impossibility of performing reliable observations in the nest selected by the pair. All the eyries were located at the front of cliffs, whether on ledges (3 sites), or in holes (6 sites). Each pair was formed of mature adults. The observation spots were always located at least 100 metres from the eyries with the assurance that the pair could not be disturbed. Observations were made with a 20-60 x telescope and 8 X binoculars. A portable tape-recorder was used to record the behavioural descriptions, the precise location of the peregrines,

and the time.

microphone

(for oral description) and a cannon microphone

Two

microphones

were

connected

to the recorder:

a lapel

pointed at the nesting cliff (for

the recording of birds vocalisations). The telescope was mainly turned towards the eyrie whenever inspected

at least one of the adults was there. to detect the presence of falcons.

The main

roosts of the site were

regularly

249 The Walsh

test was chosen

for comparisons

because

two

types

related samples were used, each subject serving as its own control. compared were drawn from symmetrical populations (tested). compare

between

vs. without

the probabilities

of data

within

two

Moreover, the samples The X2 was used to

of success of the males brooding

shifts performed

with

food bringing.

Results

Typology of the food bringing sequences The interactions occurring between the bird providing prey, its mate, its offspring (eggs or young), are the features taken into account to evolve a typology. The transfers could happen in flight, at the eyrie, or at any part of the site: these features were detailed in an initial

typology but were not pertinent

actually observed food-bringing

here. According to these criteria,

sequences were relevant.

It is worth

five types of

noting that the

occurrence of feeding is not relevant because it closely depends on the age of the young. The typology only takes into account the food-bringing sequence until the transfer to the offspring (or merely the contact with the clutch if the falcon eats at the eyrie) should the case occur: PM:

P * brings food, P transfers to Mate;

PMI:

P * brings food, P transfers to Mate, then P incubates;

PO:

P * brings food, P transfers to Offspring;

PMO: P * brings food, P transfers to Mate, then Mate transfers to Offspring;

and

PR:

P * brings food, Mate ‘refuses’ the food. * P represents the provider

Totals and types of food bringing sequences performed

according to the sex

Males performed 117 out of 184 (64%) observed food bringing sequences (Fig. I). Only two types of food transfer were performed by the females: ‘PO’ and ‘PM’. Although the total of PO food bringing sequences is higher for the females, it did not differ significantly between both sexes (n = 7, max (d5, frequently

1/2(d4

+ di’)} > 0,

N.S.).

PM occurred

among males than among females (n = 7, max {d5, 1/2(d4

more

+ d7)I < 0, P <

0.05) and ‘PMI’, ‘PMO’, ‘PR’ were specific to males.

The food bringing sequences according to the breeding period females (fig. 2%) The females performed ‘PM’ food bringing during courtship (100% of their food bringing) but less frequently than the males, and ‘PO’ from egg-pipping (attempt at feeding the pipped eggs) till fledging of the young (100% of their food bringing). No food transfers from females to males occurred outside the courtship.

250

rI

0 PR q

--”

100

PM0

I

PO

q

PM1

n

PM

l-l

80 60 40

20

n~

Females

Males

Fig. 1. Total and types of food bringing sequences according to the sex.

During

courtship,

‘PM’

is the only

food

bringing

performed

well. The PMI was specific to males in the course of incubation. the young

were

20 days old,

Once young were between bringing

sequence

‘PMO’

was the food

by males and females

as

Then, from egg-pipping

bringing

sequence

20 and 30 days old and thereafter,

mainly

‘PO’ became

till

observed.

the main food

performed.

Analysis of the food bringing

sequences

PM (P transfers to Mate) This pattern occurrence

could

will

this circumstance actual cannot

beneficiary,

when

searching

to whom

the falcon present at the site always intercepts the initial

the following

more frequently

destination

of a food

bringing

at the site. The first food was brought:

its mate.

cannot

indeed,

be inferred:

in

from the that is we

perch (ledge

or tree).

explanation:

if a peregrine

falcon

brings a prey for its mate,

it

perch close to it (not more than 2 metres away) than upon another Data do not corroborate

falcons are not significantly (Table

when the birds were in flight or perched into account

be sure that a falcon brings a prey for its mate even if this one is able to get it. We

put forward should

happen

not be taken

more frequently

this hypothesis:

perched

before

food transfers,

the

close to their mate than at a distance

I).

The food transfer to the mate may have developed from the food bringing behaviour to the site which also occurs in the sedentary pairs outside the breeding cycle. The motivation underlying the food bringing behaviour during initially - bringing a prey to the mate although mate).

However,

might

secondarily

by making (and

the contact

gradually)

courtship is thought not to be - at least it results in a transfer (triggered off by the

easier with

the mate, the courtship

get an immediate

could be especially appropriate for the males dominated come close to them during courtship.

function

of ‘coming

by the females,

food bringing together’.

but motivated

This to

251

II =

II = 6

II = 5

II = 3

YGO

F
F<60

F.571)

YGO

FGO

F<60

F<70

1 I, = 15 II = 16 II = 13 n=6

1

a

C

1

PE

Y
Y<20

Y<.lO

Periods

c

I

PE

k’s10

Ys20

YGO

Periods Fig. 2. Proportion Females,

of each type of food-bringing

(b) Males;

n = total number

relating to the sites studied: C = Courtship (17-33

eggs( f 2 days); Y = Nestling young (39-42

FM/ (P transfer

occurences.

days); 1 = Incubation

Periods and (29-30

margin

of time

days); PE = Pipped

days); F = Fledgling young (29-47

days).

to Mate, then P incubates)

Like the female, wonder

sequence according to the breeding stage. (a)

of fad-bringing

the male peregrine is able to perform

why the food bringing during incubation

incubation,

therefore we may

is specific to males. We suggest that

bringing food at this period may confer an immediate advantage to the male by allowing him to incubate the eggs. Such an advantage is not required by the females, their 25 requests for shifts were all successfully performed: the females reached the eyrie to brood whenever they wanted. The postulate underlying this explanation is the existence of an

252

TABLE 1 Comparison

of food

bringing

patterns

‘Type

PM’

occurring

during

perches close to its mate versus those where

it perches at a distance.

Pairs

At any place of the site

Close to the mate

courtship

Differences

zl

2 1

0

d7=2 d3=1

e

0

1

dl=

f

1

0

d4 = 1

:

2 1

0

d6 d2= = I2

I

1

0

d5 = 1

Total

8

where

the

supplier

(ranges)

-1

1

* n = 7, min{d3, 1/2(dl

+d4)}

= 0, N.S.

* Walsh Test.

actual

motivation

(Carlier,

of the males for incubating

since they always take a share in incubation

1993).

Analysis of data suggests that it is profitable

for a male to bring a prey to his female

in

order to obtain a brooding turn (Table 2). It is worth noting that the females are never observed eating at the eyrie during incubation, that is a prey transfer to a female results in her departure during

from

incubation

the eyrie.

Therefore,

the motivation

underlying

males’

food

bringing

may be to incubate.

PO (P transfers

to Offspring)

and

PM0

(P transfers

to Mate,

then

Mate

transfers

to

Offspring) From the occurrence males and females direct

transfers

of direct

were

(PO)

both

transfer

motivated

to young

to offspring

in the two sexes, we can infer that

to feed young.

was higher

in the

However,

females

than

the amount in the

males

of these but

not

TABLE 2 Comparison without Pairs

between

the probabilities

of success of the males brooding

Shifts with male food bringing

Shifts without

Successes

Successes

Failures

2

I

Total

shifts performed

food bringing. male food bringing Failures 1

1

0

1

1

2

1

4

2

2

0

0

3

1

2 2

1

1

1

5

1

2

1

3

0

1

0

3

12

12

14 X2 = 4.491,

df = 1, P < 0.05

with

vs.

253

100

0

% F. T. WITHOUT

l

% FEED/

F.

F.T.

90

! 80 r 70 c 60

40 30 50 /

%

20 10 1

l/l P.E.

YSlO

YIZO

Fig. 3. Percentage of the males’ food-bringing occurring at each period) performed

!~l~lil=l,~~,,~3’,

yao y$$o PERIODS

F
(out of the total number

of young out of these food-bringing

significantly.

2b clearly

when directly

lower

(PO),

hypothesis,

of the males’ food-bringing Percentage

(curve). n = the total of food-bringing observed during each period.

Figure

young were

F$70

when the female is away from the site (histogram).

of the males’ feeding

proportionally

F<60

displays

than the transfer

that

the

direct

to the female

transfer

which

by the

male

(PO)

transfers to the young

was

(PMO)

less than 20 days old. We suggest that if the male rarely feeds the young

it is because

we observed

the female

what

prevents

happened

him from

when

the absence

of their mate. The females extensive

life (Carlier,

1993)

made these occurrences

The results support

this hypothesis

able to reach the young

doing

it. In order

the males were attendance

to check this

able to reach the eyrie

during

the young

in

first days of

scarce.

(Fig. 3). Whenever

the males bringing

of less than 20 days of age in the absence

they fed - or at least began to feed - the young over 20 days old, the males (like the females)

before female

often

arrival.

let the young

a prey were

of the female When

(n = 41,

young

feed alone

were

(50% out of

males feeding). PR (Mate

‘refuses’ the food)

Female

reluctance

cially after hatching.

to leave the eyrie However,

PM0

was often

food bringing

observed sequences

were able to stay close to the offspring

while

The few refusals (PR) observed

the nestling stage happened

the females brood

for staying

- could

only observed

during

close to the young

be stronger

preventing

during

or feeding.

gives prominence

but espe-

that the females

the males from reaching

- and to prevent

than that of eating

with male as provider

incubation

demonstrate

the eyrie.

when the motivation

the male from

It is worth

to the female’s

noting

investing

of the

that PR being

domination

over the

male at the eyrie.

Discussion During

courtship

with the mate.

the function

of food

In the course of incubation,

bringing

may be to facilitate

contact

the male may bring prey to the female

behaviour

in order

254

to sit on the eggs (peregrines and females

then the young. therefore

In the presence

eggs’ (pipped

of the female,

The motivation outcome:

if a female

‘intended’

for

concerning

parental

Carrier,

obtains

her.

1993).

interactions,

bringing to

motivation

the outcome

infer

The role of the female’s

has been

emphasized

Wrege

and Cade,

1987;

Carlier

and Callo,

Furthermore,

1977;

Cramp

which

can involve

1977;

Cramp

1989;

and Simmons,

1980)

revealed

bringing

sexual

motivation.

Cade suggested a continuity usually

stops when

motivation

courtship

1980;

Herbert,

Ratcliffe,

females in landed

1980;

1970;

Nelson,

Monneret,

1992;

Wrege

Carlier,

and Cade,

of this behav~oural each one pulling motivation

pattern

at the prey.

of males is closely

may

would

have

prey to the female,

to our

of parental

duties.

is an outlet

of the

for courtship.

from courtship

According

prepared

to the female

is convenient

then to

From this point of

However,

into incubation:

of a male’s sexual impulse

mainly

easier through

observed).

to the fulfilment

by the male

This explanation

begins.

which

its

(see also

1965;

and Carlier,

were actually

in the determinism

male and female

used to transfer

and

Hubert

is related

bringing

be the only outlet

incubation

to incubate

However, between

behaviour

that food

should

and

sequences

the pair, especially

assume that the parental

assumed

prey to the female

from

Data show that males like females are likely to incubate,

the males’ internal

within Herbert

the ambivalence

view, male’s

males

bringing

male and female,

and to feed the young (all these activities food

be induced

between

of food

et al., 1991;

brood

Cade (1960)

not

of food transfers (e.g. Nelson,

put forward

to that of females.

differences

1960;

a brief struggle between

The explanations

should

and Simmons,

Gallo

descriptions

and

able even to

it does not mean that food was initially

domination

(Cade,

1989),

the brood.

a prey from a male, from

at the eyrie is sometimes

behaviour

It is misleading

1970; 1993).

food

and Callo,

the male has no access to the offspring

by the male by not leaving

underlying

eggs). Once eggs pip, males

eggs stage, Carlier

can only transfer prey to its mate. A female

refuse a prey provided

related

never eat at the eyrie containing

bring prey to feed ‘calling

to bring a

because copulation

explanation

it would

be the

lead the male to bring a prey to the female.

the

incubation

the medium

period

of food:

in making

the contacts

because the male previously

we suggest that he may have quickly

learnt to perform

prey transfers in order to sit. on the clutch. During

the nestling

in an ambivalence arousing

females’

Therefore

supported

because

nestlings

Monneret females’

aggressiveness”

siveness”. young

period, in the

the male it neither

(1974)

concluded

behaviour:

and “specific

young stimuli

hunts to appease

takes into account

nor the prey bringing

that the hatching simultaneously

of inhibitory

the female. young,

“intruders

mechanisms

This hypothesis

the few observations

to fledging

of eggs results

mean

the female

of aggrescannot

be

of males’ feeding

of

being away from the

site. Fu~hermore, when Monneret considers young as ‘intruders’, it implies that the falcon perceives its offspring in an additive form: the meaning of the young adds to that of the eggs. If we consider

that the incubation

offspring’s

- from

meaning

cannot be explained in that way. behaviour from the adults (without explanation, monopolizes

the female the young

The previous

is followed

of view

by a nestling period

- is different,

in which

the parental

the

behaviour

Hatching of young is likely to elicit specific parental reference to the previous period). According to our

(motivated for breeding, feeding and staying close to the offspring) so that she prevents the male from approaching them.

explanations

of the male’s food bringing bringing. The parental the females over their

period

the bird’s point

(Cade, - feeding

1960;

Monneret,

of the female

1974)

tend to assimilate

- to the motivation

underlying

the effect this food

motivation peculiar to males is underestimated. The dominance of mates partly conceals the actual parental motivation of the males.

255

in the

peregrine

falcon,

the evolutionary

trend

(leading

to reversed

sexual size dimor-

phism) may have resulted in a pair pattern in which both sexes show about the same parental investment in their offspring. When the young hatch, parental investment, for male and female

as well, expresses itself in both a motivation

feed. The former powerful,

monopolizes

Involvement died.

motivation

is the strongest

brooding,

the other

of both birds would

Moreover

attendance

allow

the domination

to brood

so that the dominant rather

brood

‘making

rearing

of a mate would

do’ by hunting

prejudicial

Thus the female

Furthermore, before

it might be more adaptative

assumed: falcon

female

body

domination

size (Nelson, ‘I..

adjustment

would

1970).

that the female

dominant

them.

schedule

during

is the strongest

On the other

this explanation

successful

pair

bond

to the male and when

to his subordinate

If there

for duties could

can result

trend

brooding,

Cade (I 960)

only

when

a

who

the female

the male makes a biologically

role in the pairing

by her

hand the evolutionary supports

be

breeding.

mate of the pair

be the same as that for more efficient

Therefore

a reproductively

is clearly

the duty

(1990).

so that the eggs do not have to be ‘discovered’

she feels the necessity to incubate

to establish larger

‘manages’

in the overall

that of Muller

in the pair, the mate’s aggressive competition

in the sense that she is the layer,

for the young.

too much variability

supports

was no clear domination to the brood.

to

larger and more

by a single mate if one of the parents

avoid

and duties at the site. This hypothesis

and a motivation

mate,

adequate

situation.”

Acknowledgements We are grateful 1989.

to Fransois

Delage

for his valuable

We also thank Jacques Lauga for his advice

assistance in the field during

about

spring

data processing.

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