5 Aviary Brood Sibling dyad Same preferred

tutor? N°'of sharedelements

Cl 2 F3 - W15 NO 0 “ ) Cl 4 F4 - FI 2 YES 9 1) C2 1 W1 - W2 NO 5 2) C2 1 W1 - W5 YES 5 1) C2 1 W2 ~ W5 NO 0 - ) C2 2 W14 - W13 YES 8 1) C2 2 W14 - W25 YES 7 1) C2 2 W13 - W25 YES 7 1) C2 3 F3 - F4 NO 0 -) C2 4 F15 - F13 NO 5 3) C2 4 F15 - F2 NO 1 + ₁₎ C2 4 FI 3 - F2 NO 0 -)

In brackets - the number of tutors contributing to the shared elements.

a

13 Cl Brood 4. F4m & F12m. Both learnt song only from FLGm, copying nine and 11 elements from him respectively. These elements were generally reproduced in the same order as in the tutor’s song; changes from the original sequence were not identical in the songs of the two juveniles.

C2 Brood 1, Wlm, W2m & W5m. W1 and W5 both showed a preference for the song of their father, while W2 preferred WDGm, Looking in more detail, five elements of the songs of W1 and W2 had a common origin, five were shared between W1 and W 5 , and none were shared between W2 and W 5 . The shared elements of W1 and W5 (all copied from the father) appeared in a different sequence in their respective songs. However, the five shared by W1 and W2 were learnt in exactly the same order. Of particular significance is the last of these

elements, which was taken from the song of FOm, while the others were all derived from WDGm (and were copied in the original order). Given its position in the song of W 2 , the probability of the element from FOm occupying an equivalent position in that of W1 is if the block taken from WDGm is considered as a single unit (and therefore unlikely to have been split). However, this does make the assumption that any element can theoretically occupy any position in a song; this may well be unrealistic (see Ten Cate and Slater 1991) .

02 Brood 2. W14m, W13m & W25m. All three learnt only from their father, each copying eight elements from him, with seven or eight shared. The elements all tended to be arranged in the same order as in his song, (This does not imply that the young were influencing each other in their song development; they could all have independently had a

1

strong preference for the father’s song, in which case the sharing of a string of elements would be quite likely).

C2 Brood 3, F3m & F4m, No elements in common. C2 Brood 4, F15m, F13m & F2m. Each selected a different "preferred" tutor. All learnt at least two elements of their father’s song. F15 and F13 shared five elements, copied from three different tutors, F13 and F2 had no elements in common, while FI5 and F2 shared at least one. These results show that siblings do not necessarily learn from the same song models. The similarity of the songs of sibling pairs can be categorised as follows:

1. Few (two or less), or no, shared song elements.

F3 & W15 (Cl), W2 & W5, F3 & F 4 , F13 & F 2 , F15 & F 2 . 2. Several shared elements, copied from the same tutor.

F4 & F12 (Cl), W1 & W5, W14 & W13, W14 & W25, W13 & W25, 3. Several shared elements, copied from more than one tutor.

W1 & W2, F15 & F13,

The likelihood of a direct sibling influence on song

development increases through groups 1-3, Certainly, where no elements were shared between a pair of siblings, a weaker behavioural association between the birds might have been

I

1

I

expected. This is considered later.

■COMPABJ . SONGiS..OF.NOtLz&IBMkQS

The following dyads of non-sibling males had several song elements in common (the number shared is given in brackets):

15

C2 - FIS & F3 (7), F13 & F4 (4). J

In these cases, the shared elements occurred either in the same order as in the model songs, for each bird of the pair, or the sequence was altered, but in a different manner.

There is nothing here to suggest that the common source of elements had to do with anything other than the independent selection of the same song tutor.

J

However, there were cases in C2 where there is some reason ..A to suspect the existence of an influence between juveniles, #

J

on their song development. The song of F 2 , from brood 4 ;; contained the same five-element string, derived from two

tutors, as that shared by siblings W1 and W 2 . Also, W2 and F4 had in their songs the sequence:

Element 3 (from FLPm) - E4(FLPm)/El(FDGm) - E2(FDGm). In both situations, it would seem quite unlikely that such a pattern would have emerged by chance, where elements were being copied from more than one tutor.

MAMSJ^--OF MHAyiOUR.QF '£H1_AVIARY BIRDS

W h A t . . Qlo.sg.., is.^.u.al t. t h e

Good indicators of the existence of strong sexual or social bonds between pairs of zebra finches are nest sharing, and clumping and allopreening (Butterfield 1970). At least one of these behaviours was recorded at some stage in all eight breeding pairs, but between no other adult combinations

I

■

•il and FDGm from C2). In both cases the relationship between f;

i

-i such that aggressive tendencies are largely suppressed and 3 sexual ones enhanced",

Between adults and juveniles, such associative behaviours only occurred between parents and their offspring, but with

Î again two exceptions, FDGm and Wlf (from Cl), and WRm and i

1 W4f ( from C2 ) . These birds formed pair bonds during the

observation period (from approximately 50 and 47 days of age respectively for the females). Paired status was determined independently in these, and other such cases, by

observations of sexual behaviour, such as persistent directed song from male to the female, soliciting by the female, copulations and by joint nesting behaviour (nest building and defence, and incubation).

Between juveniles, clumping, allopreening and/or the

simultaneous occupation of a nest box were recorded in 53 of the 66 sibling dyads, but between only 25 of 225 non-sibling dyads (chi-squared = 124.5, df = 1, p < 0.001), Of these latter 25, between seven and nine cases involved opposite- sexed offspring that ultimately formed pair bonds.