0 November 1965 (breeding)

Harvey I. Fisher, Uni- Cursory survey Fisher ( 1965)

and 3 0 November 1965 (breeding)

*** Recaptured at Kure 15 January 1964 (breeding).

*** Recaptured at Kure 14 December 1965 (breeding) and 4 December

1968 (breeding).

BLACK-FOOTED x LAYSAN ALBATROSS Diomedea n i g r i p e s

x

immutabilis A h y b r i d a l b a t r o s s was c o l l e c t e d on 26 J a n u a r y 1964. T h i s

i n d i v i d u a l ,

a

female, resembled a Black-footed A l b a t r o s s i n plumage and b i l l s i z e , b u t had a l i g h t e r - c o l o r e d head t h a n u s u a l , a w h i t i s h abdomen, and a horn-colored b i l l s i m i l a r t o t h a t of t h e Laysan.

NORTHERN

FUZMAR

Fulmarus g l a c i a l i s r o d g e r s i i

I n 1964 f o u r dead Fulmars were c o l l e c t e d : one each on

16

January, 26 February, 28 March, and 3 0 March. These l a t t e r two b i r d s were f l a a t i n g i n t h e s u r f o f f t h e west p o i n t .

Only t h e January specimen, a dark-phase i n d i v i d u a l , was prepared a s a s t u d y s k i n . The c o l o r phase of t h e o t h e r s was n o t r e c o r d e d .

m l m a r s have been a l s o recorded i n t h e Northwestern Hawaiian I s l a n d s from Midway A t o l l and French F r i g a t e Shoals (Clapp and Wood- ward,

1968).

BONIN PETREL Pterodroma

k.

hypoleuca

S t a t u s

Abundant w i n t e r - s p r i n g b r e e d e r ; maximum e s t i m a t e 2,500. P r e s e n t from e a r l y August t o June. One J u l y r e c o r d . Peak p o p u l a t i o n s p r e s e n t from September o r October through mid-March. Breeds from l a t e January t o l a t e J u n e .

P o p u l a t i o n s

Munter

a able

BP-1) p r o b a b l y overlooked Bonin P e t r e l s d u r i n g h i s b r i e f d i u r n a l s t a y , w h i l e Wetmore gave no numerical e s t i m a t e s o

it i s impossible t o determine whether o r not t h e Bonin P e t r e l popula- t i o n h a s changed n u m e r i c a l l y s i n c e t h e e a r l y p a r t of t h i s c e n t u r y . Robbins' October

1959

e s t i m a t e , made, p r i o r t o t h e a l t e r a t i o n of t h e i s l a n d , i s i n g e n e r a l agreement w i t h r e c e n t POBSP ones (Table BP-2), s u g g e s t i n g t h a t t h e LORAN s t a t i o n c o n s t r u c t i o n had l i t t l e e f f e c t on t h e p o p u l a t i o n s i z e .

Recent POBSP e s t i m a t e s i n d i c a t e d a maximum of 2,000 t o 2,500

i n d i v i d u a l s u s i n g t h e i s l a n d d u r i n g

a

two week p e r i o d . These e s t i m a t e s , however, a r e c o n s i d e r e d e x e l i a b l e and t h e t o t a l p o p u l a t i o n may be c o n s i d e r a b l y h i g h e r . For example, d u r i n g t h e 1963-64 b r e e d i n g season 1 , 6 2 0 Bonin P e t r e l s , about 900 l e s s t h a n t h e h i g h e s t e s t i m a t e , were banded. The comparable f i g u r e s f o r t h e n e x t season were 1,005 and c a . 1,000, r e s p e c t i v e l y . It i s u n l i k e l y t h a t 64 p e r c e n t of t h e t o t a l

-

p o p u l a t i o n u s i n g t h e i s l a n d i n 1963-64, and 50 p e r c e n t i n 1964-65, were banded; t h e s e maximum e s t i m a t e s were probably t o o s m a l l .

114

Table BP-1. P r e v i o u s r e c o r d s of Bonin P e t r e l s o n Green I s l a n d , Kure A t o l l .

P o p u l a t i o n

Date of Survey E s t i m a t e Breeding S t a t u s , Remarks, References

1915

March 28

- -

1918

September

15

?

1923 A p r i l 17-22

1957

June

5 1959

October 3-8 1960 March

28 1961

January 19-21

September 12-14 1962 February 2-4

August 6-8

1963

February 3-7

(Munter, 1915).

Offshore (R.G. 45, N a t . Archives, Report of Commanding O f f i c e r U.S.S. Hermes t o Commandant 1 4 t h Naval D i s t r i c t ) .

None found n e s t i n g (Wetmore, ms.).

(Kenyon and Rice, 1 9 5 8 ) . (Robbins,

1966:

5 3 ) . (Robbins,

1966:

5 3 ) . (Robbins,

1966:

5 3 ) .

I 9 e s t i n g (udvardy and Warner,

1964:

2)

(Robbins, ^r-

Even more i l l u s t r a t i v e of t h e d i f f i c u l t y i n esti1.1ating t h e s i z e of Bonin P e t r e l p o p u l a t i o n s was a r o o s t i n g s t u d y conducted from 11 February t o 14 A p r i l

1969

( d e t a i l s t o be p u b l i s h e d e l s e w h e r e ) . On a l t e r n a t e n i g h t s a t

s.

2100 hours a s many Bonin P e t r e l s a s p o s s i b l e found r o o s t i n g o r bur- rowing i n e i t h e r t h e n o r t h antenna f i e l d o r t h e open a r e a j u s t s o u t h of t h e b a r r a c k s were c a p t u r e d . Unbanded i n d i v i d u a l s were banded and t h e band numbers of p r e v i o u s l y banded ones were r e c o r d e d . During t h i s s t u d y 1,747 d i f f e r e n t Bonin P e t r e l s were handled; y e t t h e maximum number handled on any s i n g l e n i g h t was o n l y 213. Obviously t h e r e was a c o n s i d e r a b l e amount of t u r n o v e r . Usually a t l e a s t 90 p e r c e n t of t h e b i r d s c a p t u r e d on any n i g h t had n o t been handled t h e p r e v i o u s n i g h t nor on any o t h e r given n i g h t , and a t l e a s t 40 p e r c e n t had n o t been handled p r e v i o u s l y d u r i n g t h e s t u d y p e r i o d . S i n c e o n l y 451 Bonins were c a p t u r e d more t h a n once, t h e Kure p o p u l a t i o n was h i g h l y t r a n s i t o r y . Based on an average d a i l y t o t a l t u r n - over r a t e of 50 p e r c e n t , and a d a i l y p o p u l a t i o n of 100 b i r d s from September through A p r i l , t h e t o t a l number of Bonin P e t r e l s u s i n g Kure

a t

l e a s t once would be 12,000. F i g u r e BP-1 shows t h e number of Bonin P e t r e l s c a p t u r e d

each n i g h t d u r i n g t h i s s t u d y . This

i s

a b e t t e r i n d i c a t i o n of t h e s i z e of t h e p o p u l a t i o n than t h e semi-monthly e s t i m a t e s .

Table BP-2. POBSP semi-monthly estimates of Bonin P e t r e l s on Green Island, Kure A t o l l , 1963-69.

1963 1964 1965

1966

1967 1968 1969

January

1-15 16-31

February

1-15

16-28 March

1-15 16-31

A p r i l

1-15

16-30

June

1-15

16-30 J u l y

1-15 16-31

August

1-15

September

1-15

16-30 October

1-15

16-31 November

1-15

16-30 December

1-15 16-31

X B i r d s p r e s e n t , number unknown.

S i n c e t h e maximum n e s t count was 500, most Bonin P e t r e l s u s i n g t h e i s l a n d were non-breeders, probably b i r d s from o t h e r i s l a n d s ( s e e Banding and ~ o v e m e n t s ) . This would account, i n p a r t , f o r t h e r e l a - t i v e l y s t a b l e p o p u l a t i o n s i z e d e s p i t e t h e almost complete b r e e d i n g f a i l u r e of t h i s s p e c i e s .

Annual Cycle

Bonin P e t r e l s r e t u r n e d t o t h e a t o l l i n e a r l y August ( e a r l i e s t r e c o r d s :

6

August 1962, 1 0 August

1965,

and

8

August 1968). A t f i r s t o n l y a few i n d i v i d u a l s were p r e s e n t b u t by September o r October t h e y were abundant. Peak p o p u l a t i o n s were p r e s e n t through mid-Marckl. The s i z e of t h e p o p u l a t i o n t h e n d e c r e a s e d r a p i d l y and by May few p e t r e l s r o o s t e d on t h e i s l a n d . U s u a l l y a l l b i r d s had d e p a r t e d by l a t e May

( l a t e s t r e c o r d s : 24 May

1965,

25 May

1966,

4 June

1967,

and

Zi

May 1968).

I n

1969,

when young Bonins f l e d g e d , a d u l t s were p r e s e n t u n t i l a t l e a s t mid-June

) .

The J u l y

1968

r e c o r d i s u n i q u e .

Although c o u r t i n g and burrowing began s h o r t l y a f t e r t h e a d u l t s r e t u r n e d , egg l a y i n g d i d n o t begin u n t i l l a t e J a n u a r y

(23

J a n u a r y

1964

and

1965

and ca. .17 J a n u a r y 1 9 6 9 ) . A p p a r e n t l y most eggs were l a i d i n l a t e J a n u a r y a n d e a r l y February. I n

1969

a female w i t h an egg i n t h e o v i d u c t was c a p t u r e d on

19

February. T h i s was i n accordance w i t h t h e t e r m i n a t i o n of egg l a y i n g f o r o t h e r y e a r s .

Eggs were known t o have hatched o n l y i n

1969,

when t h e f i r s t ones h a t c h e d i n e a r l y March and t h e l a s t ones i n e a r l y A p r i l . Most eggs h a t c h e d from

E.

1 E t o 20 March. The f i r s t c h i c k s f l e d g e d i n e a r l y June and t h e l a s t ones t h e t h i r d week of June. It i s n o t known how many y e a r s w i l l e l a p s e b e f o r e t h e s e young Bonin P e t r e l s r e t u r n t o t h e a t o l l .

N e s t i n g Success

From 1964 through

1968

no young Bonin P e t r e l s were known t o have f l e d g e d from t h e a t o l l . I n

1968,

however, one young may havebeen suc- c e s s f u l l y r e a r e d ,

as

on

17

J u l y an a d u l t was c a p t u r e d t h a t r e g u r g i t a t e d stomach o i l when handled,

a

s i g n i n most p r o c e l l a r i i f o r m e s t h a t young a r e p r e s e n t . A c a r e f u l study of burrows i n t h e a r e a r e v e a l e d no young.

The o n l y s u c c e s s d a t a were f o r

1969

when t h r e e s t u d y a r e a s , one i n t h e open a r e a j u s t s o u t h of t h e b a r r a c k s , one i n t h e n o r t h antenna f i e l d , and one i n t h e s o u t h a n t e n n a f i e l d , were e s t a b l i s h e d i n February. The former a r e a was u n p r o t e c t e d ; t h e l a t t e r two a r e a s were poisoned w i t h Warfarin t o p r o t e c t them a g a i n s t P o l y n e s i a n r a t s .

I n t h e a r e a near t h e b a r r a c k s 20 n e s t s were marked i n mid-February.

By

25

February t h e y had a l l d i s a p p e a r e d due t o r a t p r e d a t i o n . The eggs had been broken and t h e s h e l l s were o f t e n found o u t s i d e t h e burrow.

Four eggs of t h e

9

(44.4 p e r c e n t ) marked i n t h e s o u t h antenna f i e l d h a t c h e d . Two of t h e s e young (50 p e r c e n t ) f l e d g e d .

I n t h e n o r t h antenna f i e l d 24 of

40

(60 p e r c e n t ) marked eggs h a t c h e d and 1 0 of t h e s e c h i c k s f l e d g e d (25 p e r c e n t of a l l eggs and 41.7 p e r c e n t of eggs t h a t h a t c h e d ) . Rats d e s t r o y e d a few of t h e n e s t s and o t h e r s were probably l o s t

a t

t h e i n i t i a l d i s t u r b a n c e , b u t t h e cause of l o s s l a t e r i n t h e y e a r was unknown.

An e s t i m a t e d 8 0 young Bonin P e t r e l s , a l l from t h e c e n t r a l p l a i n , f l e d g e d i n

1969.

Most of t h e s e b i r d s were o u t s i d e t h e p r o t e c t e d a r e a s , s o t h e y were s u b j e c t e d t o p o s s i b l e r a t p r e d a t i o n . Whether t h e poisoning program was s u f f i c i e n t t o e l i m i n a t e t h e s e mammals from t h e c e n t r a l p l a i n , o r whether t h e p o p u l a t i o n was n a t u r a l l y reduced, i s unknown, b u t t h e d a t a from t h e s t u d y a r e a s s t r o n g l y s u g g e s t t h a t P o l y n e s i a n r a t s were t h e major f a c t o r i n t h e b r e e d i n g f a i l u r e of t h i s s p e c i e s a t Kure A t o l l .

Ecology

Bonin P e t r e l s o c c u r r e d mainly

i n

t h e a r e a j u s t s o u t h of t h e b a r r a c k s , t h e s m a l l a n t e n n a f i e l d by t h e t e n n i s c o u r t , and a t t h e n o r t h e r n edges of t h e n o r t h and s o u t h antenna f i e l d s .

The major b r e e d i n g h a b i t a t was t h e s a n d - E r a g r o s t i s a s s o c i a t i o n . Here t h e y dug burrows from one t o s i x f e e t long, g e n e r a l l y under a g r a s s clump. Some b i r d s , p o s s i b l y young ones, dug shallow t r e n c h e s , b u t t h e s e were n o t u t i l i z e d f o r b r e e d i n g . The s i n g l e egg was l a i d n e a r t h e f a r end of t h e burrow. Other burrows were found under Scaevola n e a r t h e g r a s s y a r e a s , i n t h e Tribulus-covered c e n t r a l p l a i n , and i n

open a r e a s of t h e c e n t r a l r o o s t . Not a l l of t h e s a n d - E r a g r o s t i s a r e a was used by t h i s s p e c i e s . I n

1969

t h e m a j o r i t y of young Bonin P e t r e l s f l e d g e d from burrows a l o n g t h e edges of Scaevola a t t h e n o r t h e r n end of t h e s o u t h antenna f i e l d .

Banding and Movements

Robbins banded

48

a d u l t Bonin P e t r e l s and t h e POBSP banded 6,050.

The low r e c a p t u r e r a t e s of t h e s e b i r d s (Table BP-3) a g r e e w i t h t h e p r e v i o u s d i s c u e s i o n of t h e l a r g e amount of t u r n o v e r i n t h i s s p e c i e s . E i g h t y n e s t l i n g Bonin P e t r e l s were banded i n 1969.

S i n c e Bonin P e t r e l s burrow and when t h e y a r e r o o s t i n g on l a n d t h e i r l e g s a r e i n a l m o s t c o n s t a n t c o n t a c t w i t h t h e ground, bands a r e s u b j e c t e d t o heavy a b r a s i o n . A f t e r t h r e e y e a r s o r s o t h e bands become s o t h i n t h e y f a l l o f f . Thus r e c a p t u r e s a f t e r t h r e e y e a r s a r e lower t h a n would be e x p e c t e d .

Three Kure-banded Bonin P e t r e l s were r e c a p t u r e d a t P e a r l and Hermes Reef: an a d u l t banded on 1 0 March

1965

was r e c a p t u r e d on S e a l

w Fi w

5

a a,

3

i-' a m 0 w k

a

c m

ri

2

C) 4

a, k

2

4 m

"2

3 a

m

m 6

a

w a.

2 ?A ""

m m rim w m k ri i-' w

-

C4- "2

c

w .A M s2 6 0 i-'

2

%. u 0 Fi w m a w C) VI m m Fi

a

w w

2: +

w a Fc m a 0 X w

a-

m I Pi

m

w ri D m u

I s l a n d

8

days l a t e r and t h e n c a p t u r e d a t Kure on 23 November

1965;

a n o t h e r a d u l t banded on 23 November 1964 was r e c a p t u r e d on S e a l I s l a n d on

19

March

1965;

and a n a d u l t banded on 21 October 1964 was c a p t u r e d on S o u t h e a s t I s l a n d on

16

March

1965.

Twelve non-breeding Bonin P e t r e l s banded on o t h e r i s l a n d s were r e c a p t u r e d a t Kure (Table BP-4).

T a b l e

BP-4.

A d u l t Bonin P e t r e l s banded on o t h e r i s l a n d s and r e c a p t u r e d a t Kure A t o l l .

P l a c e of Banding Date of Banding Date of Recapture

Midway A t o l l Midway A t o l l Midway A t o l l Midway A t o l l Midway A t o l l

P e a r l and Hermes Reef P e a r l and Hermes Reef P e a r l and Hermes Reef L i s i a n s k i

L i s i a n s k i L i s i a n s k i

French F r i g a t e S h o a l s

KEMDEC PETREL

29 March 1960

5

February 1962

6

February 1962

7

December 1963

17

December 1963

16

March

1965 7

March 1963

1

_March

1963

1 2 March 1965 1 2 March

1965 U

March

1965

1 2 March

1967

On t h e evening of 20 A p r i l 1923 Wetmorf

3

October 1964 3 0 November 1964

8

February

1966 9

September

1966 15

September

1966

1 0 September

1966

11 February

1966 8

J a n u a r y

1965

25 February

1969 13

March

1969

23 A p r i l

1969

27 August

1968

Pterodroma n e g l e c t a c o l l e c t e d a male, dark- phase Kermadec P e t r e l a s i t - f l e w o v e r t h e c e n t r a l p l a i n .

noth her

b i r d , p o s s i b l y t h i s s p e c i e s o r t h e s i m i l a r H e r a l d P e t r e l (Pterodroma armon'oniana h e r a l d i c a ) , was s e e n f l y i n g o v e r Green I s l a n d on

31

J u l y

d e s c r i b e d t h i s i n d i v i d u a l a s f o l l o w s : " s i z e and b u i l d o f a t r o p i c b i r d , l i g h t e r brown on back t h a n a Wedge-tailed Shearwater, v e r y s h a r p brown t o w h i t e demarcation l i n e on b r e a s t l i k e Brown Boobies, r e s t of u n d e r p a r t s v e r y w h i t e , white underwings."

Kermadec P e t r e l s o c c u r commonly a t s e a i n t h e c e n t r a l P a c i f i c .

MJRPHY

'

S PETREL Pterodroma u l t i m a

Ludwig c o l l e c t e d a female Murphy's P e t r e l on

7

October

1963

a s it f l e w over t h e c e n t r a l p l a i n .

Murphy's P e t r e l s have a l s o been r e c o r d e d i n t h e Northwestern Hawaiian I s l a n d s a t French F r i g a t e S h o a l s (Clapp and Woodward,

1968).

BULWER' S PETREL Bulweria b u l w e r i i On 11 September 1964 DuMont saw a s m a l l a l l - d a r k b i r d w i t h a wedge-shaped t a i l and a l i g h t band a c r o s s t h e upper wing s u r f a c e g l i d i n g over Scaevola. DuMont acknowledged t h a t t h i s i n d i v i d u a l may have been a young Brown Noddy r a t h e r t h a n a Bulwer's P e t r e l ; hence, t h e occurrence of t h i s s p e c i e s a t Kure i s c o n s i d e r e d hypo- t h e t i c a l

.

WEDGE-TAILED SHEARWATER P u f f i n u s a a c i f i c u s

S t a t u s

Abundant summer-fall b r e e d e r ; 500-1,000 p a i r s a n n u a l l y . P r e s e n t from March t o e a r l y December w i t h peak p o p u l a t i o n s from A p r i l through October. Breeding b e g i n s i n June and c o n t i n u e s through e a r l y December.

P o p u l a t i o n s

E s t i m a t i n g t h e s i z e of t h e Wedge-tailed Shearwater p o p u l a t i o n was d i f f i c u l t , n o t o n l y because of t h e i r f o s s o r i a l and n o c t u r n a l h a b i t s , b u t a l s o because t h e y bred under t h e dense S c a e v o l a . Most e s t i m a t e s were based on t h e o b s e r v e r ' s judgment o r on banding d a t a , r a t h e r t h a n on any c o n s i s t e n t sampling. However, i n 1967 and

1968

a method was u t i l i z e d t h a t allowed comparison of t h e p o p u l a t i o n s i z e on a weekly and y e a r l y b a s i s . Once a week, a f t e r dark, Wedge-tailed Shearwaters were counted i n t h e c e n t r a l p l a i n and t h e major b r e e d i n g a r e a s o u t h of t h e b a r r a c k s . It was assumed t h a t t h i s number r e p r e s e n t e d about 1 0 p e r c e n t of t h e t o t a l p o p u l a t i o n . T h i s e s t i m a t e took i n t o a c - count t h e l a r g e r a r e a where t h e s p e c i e s occurred, t h e p r e s e n c e of u n d e t e c t e d b i r d s i n burrows, and d a i l y t u r n o v e r .

During 1964, 2,481 a d u l t s were banded. If t h i s s p e c i e s was s i m i l a r t o t h e o t h e r p r o c e l l a r i i f o r m e s on t h e i s l a n d , t h e t o t a l popu- l a t i o n u s i n g t h e i s l a n d each y e a r was a t l e a s t twice t h i s f i g u r e . A L i n c o l n Index c a l c u l a t i o n a l s o suggested t h a t t h e p o p u l a t i o n s i z e was a t t h i s l e v e l .

In 1965, 173

of t h e 404 Wedge-tails handled had been banded i n 1964 a s b i r d s i n a d u l t plumage, t h u s :

173 =

2,481

where x = t o t a l p o p u l a t i o n .

GX

^X

T h e r e f o r e , x = 5,794. Thus POBSP o b s e r v a t i o n s i n d i c a t e d a t o t a l y e a r l y p o p u l a t i o n of 5,000-6,000 i n d i v i d u a l s u s i n g t h e i s l a n d . An estimated 1,000 t o 2,000 Wedge-tails b r e d each y e a r . Data a r e inadequate t o determine how many of t h e non-breeding b i r d s u s i n g t h e i s l a n d were Wedge-tails t h a t had b r e d p r e v i o u s l y a t Kure o r were s u b a d u l t s r a i s e d a t Kure t h a t had n o t bred y e t .

The m a j o r i t y of t h e Kure p o p u l a t i o n was l i g h t - p h a s e d . Only one a d u l t of 137 (0.73 p e r c e n t ) handled i n

1967

was a dark-phase morph.

Comparable f i g u r e s f o r

1968

and

1969

were 0 . 6 9 p e r c e n t and 0.43 p e r c e n t , r e s p e c t i v e l y . Only

19

dark-phase b i r d s ( o u t of 4,319) were banded by t h e POBSP.

Comparison of e a r l i e r o b s e r v a t i o n s ( T a b l e WTS-1) w i t h POBSP e s t i m a t e s

able

WTS-2) i s of l i m i t e d v a l u e , b u t t h e a v a i l a b l e d a t a t e n d t o i n d i c a t e no s i g n i f i c a n t change i n t h e s i z e of t h e p o p u l a t i o n d u r i n g t h i s c e n t u r y . The major b r e e d i n g a r e a was always i n t h e c e n t r a l p l a i n , an a r e a t h a t was n o t g r e a t l y a l t e r e d by t h e c o n s t r u c - t i o n of t h e LORAN s t a t i o n . Whether more Wedge-tails breed under Scaevola now t h a n i n 1923 i s n o t known.

Table WTS-1. P r e v i o u s r e c o r d s of Wedge-tailed S h e a r w a t e r s on Green I s l a n d , Kure A t o l l .

P o p u l a t i o n

Date of Survey E s t i m a t e Breeding S t a t u s , Remarks, References

1915

March 28 1923 A p r i l 17-22 1957 June

5 1959

^October

3-8

1960 March 28 1 9 6 1 J a n u a r y 19-21

September 12-14

1962 February 2-4 August

6-8

1963 Februa-~r 3-7

Annual Cycle

- -

3 00 common

5,000 common

0

?

0 1,000 0

(Munter, 1 9 1 5 ) .

C a l l i n g and burrowing (Wetmore, m s .

) .

Numerous burrows

e en yon

and Rice,

1958:

1 8 9 ) .

Young ( ~ o b b i n s ,

1966:

5 3 ) . ( ~ o b b i n s ,

1966:

^{5 3 ) .}

(Robbins,

1966:

5 3 ) .

Hundrede of burrows ( ~ d v a r d y and Warner, 1964: 2 ) .

(Robbins,

1966:

^{5 3 )}

.

(Robbins,

1966:

5 3 ) . (Robbins,

1966:

5 3 ) .

Wedge-tailed S h e a r w a t e r s were f i r s t s e e n f l y i n g o v e r t h e i s l a n d on 2 March 1964, 1 9 March

1965,

and

17

March

1969.

The p o p u l a t i o n i n - c r e a s e d i n s i z e r a p i d l y and by t h e end of March hundreds were p r e s e n t . A p p a r e n t l y t h e l a r g e s t p o p u l a t i o n s were p r e s e n t from A p r i l through

October. The

1967

and

1968

c o u n t s ( ~ i g . WTS-1) s u g g e s t e d t h a t Wedge- t a i l s o c c u r r e d on t h e i s l a n d most commonly p r i o r t o egg l a y i n g and

Table WTS-2. POBSP semi-monthly estimates of Wedge-tailed Shearwaters on Green Island, Kure Atoll, 1963-69.

January

1-15 - ^{0 0} - - - ⁰

16-31 - ⁰ o - - - o

February

1-15 - o o o o - o

16 - ^{28 0 0 0} - - - ^O

March

1-15 - ^{300 0} - - 0

16 -3 1 - ^{1,750 300 -}

^K

^{2 1,000}

April

1-15 - ^{3,500 1,000} - - ^5,000

16-30 - ^{3,500 1,000 750} - - ^5,000

June

1-15 - 2,500 2,000 1,750 2,330 1,260 5,000 16-30 - ^2,500 2,000 1,750 2,070 1,140 +

August

1-15 - ^2,000 2,000 2,500 - ^3,790 -

16-31 - ^2,000 - ^2,000 - ^5,410 -

September

1-15 - ^2,000 - ^2,000 - ^2,440 -

16-30

x

2,000 - ^2,000 - ^3,530 -

October

1-15 * ^{3,000 -} - -

x

-

16-31 * ^3,000 - - -

^K

-

November

1-15 750 3,000 - ^- -

^K

-

16-30 75 50 800 - ^-

^K

^-

December

1-15

K

0 1 - -

^K

-

16-31 o o - ^{o o} -

* ^Birds present, number unknown.

h a t c h i n g , and l e a s t commonly d u r i n g t h e i n c u b a t i o n p e r i o d . By November t h e p o p u l a t i o n began t o d e c r e a s e and a l l Wedge-tails had l e f t by t h e middle of December.

Although c o u r t i n g and burrowing began s h o r t l y a f t e r t h e a d u l t s r e t u r n e d t o t h e i s l a n d , egg l a y i n g d i d n o t b e g i n u n t i l June (11 June

1965, 17

June

1966, 8

June 1967,

18

June

1968,

and 1 2 June 1969).

E v i d e n t l y peak egg l a y i n g occurred t h e l a s t two weeks of June and i n e a r l y J u l y . Some eggs were probably l a i d a s l a t e a s t h e t h i r d week of J u l y . No y e a r l y d i f f e r e n c e s i n t h e t i m i n g o f peak egg l a y i n g were e v i d e n t .

The f i r s t n e s t l i n g s were found on 3 1 J u l y 1964, 3 0 J u l y

1965,

e a r l y August

1966,

and

9

August

1968.

Hatching c o n t i n u e d a t

l e a s t through August. Young Wedge-tails began t o f l y

99

t o 111 days ( 2 ~ 1 0 3 , n = l o ) a f t e r h a t c h i n g . Thus f l e d g i n g began i n l a t e October and was completed by e a r l y December. Young Wedge-tailed Shearwaters d i d n o t r e t u r n t o t h e a t o l l u n t i l t h e y were

s.

² y e a r s o l d .

N e s t i n g Success

I n 1964 50 n e s t s w i t h one egg each were s t u d i e d t o determine h a t c h i n g and f l e d g i n g s u c c e s s . Forty-seven eggs (94 p e r c e n t ) hatched and 4 0 n e s t l i n g s f l e d g e d (80 p e r c e n t of

a l l

eggs l a i d and

85.1

p e r c e n t of t h e eggs t h a t h a t c h e d ) . Seven n e s t l i n g s d i e d b e f o r e f l e d g i n g . One was k i l l e d by an a d u l t d u r i n g d e f e n s e of i t s n e s t , one was aban- doned, and t h e remaining f i v e were s u s p e c t e d v i c t i m s of r a t p r e d a t i o n .

I n some y e a r s h a t c h i n g s u c c e s s may be c o n s i d e r a b l y lower. For example, i n August

1968

o n l y 11 of 178

(6.2

p e r c e n t ) a c t i v e Wedge- t a i l e d Shearwater burrows checked i n t h e c e n t r a l p l a i n c o n t a i n e d eggs o r c h i c k s . Whether a l l t h e s e burrows once had eggs which were d e s t r o y e d , o r whether o n l y a small number of t h e burrows were u t i l i z e d by t h i s s p e c i e s , was n o t determined, b u t i t s u g g e s t s t h a t n e s t l o s s may be heavy. Broken eggs w i t h t y p i c a l r a t openings a t t h e ends were commonly found

i n

t h e c e n t r a l p l a i n .

An e s t i m a t e d 1 , 0 0 0 young i n 1964 and 400 i n

1965

f l e d g e d .

Wedge-tailed Shearwaters bred mainly i n t h e c e n t r a l p l a i n and i n t h e g r a s s y a r e a j u s t s o u t h of t h e b a r r a c k s . Here t h e y dug burrows, g e n e r a l l y a t t h e base of

Eragrostis

o r o t h e r v e g e t a t i o n . Some burrows were a l s o found under S c a e v o l a .

Other Wedge-tails l a i d t h e i r egg on t o p of t h e ground under Scaevola, where l i t t l e o r no d i r e c t s u n l i g h t p e n e t r a t e d . G e n e r a l l y t h e egg was p l a c e d i n a shallow t r e n c h r a t h e r t h a n on f l a t ground.

S i x t y n e s t s of t h i s t y p e were found from 24 t o

28

June

1967,

i n d i c a t i n g t h a t t h e y were n o t uncommon. They were found wherever t h e r e was a con- t i n u o u s growth o f Scaevola b u t appeared t o be more common i n t h e n o r t h r o o s t .

When t h e y were n o t a t s e a , i n burrows, o r f l y i n g over t h e i s l a n d , Wedge-tails r o o s t e d i n t h e same a r e a s where t h e y bred and a l o n g t h e beach-Scaevola ecotone.

Banding and Movements

Robbins banded 235 a d u l t Wedge-tailed Shearwaters and t h e POBSP banded 4,319. The p e r c e n t a g e of t h e s e b i r d s r e c a p t u r e d a t Kure was r e l a t i v e l y s m a l l

a able

WTS-3). I n some y e a r s ( e . g . , 1967 and 1968) l i t t l e e f f o r t was expended i n c a p t u r i n g t h i s s p e c i e s , r e s u l t i n g i n lower r e c a p t u r e r a t e s , b u t even i n y e a r s when l a r g e numbers were handled ( e . g . , 1964,

1965, 1969),

t h e y were low, s u g g e s t i n g a h i g h r a t e of t u r n o v e r . An a d u l t Wedge-tailed Shearwater b a n d ~ d t h e n i g h t of 12-13 March

1964

was r e c a p t u r e d t h e n e x t n i g h t on S o u t h e a s t I s l a n d , P e a r l and Hermes Reef, 135 n a u t i c a l m i l e s t o t h e s o u t h e a s t .

Three hundred and seven n e s t l i n g Wedge-tailed Shearwaters were banded

(4

i n

1959, 5

i n 1963, 237 i n 1964,

57

i n

1965

and 4 i n

1966).

Three of t h e

1964

c o h o r t s were r e c a p t u r e d i n subsequent y e a r s a t Kure:

1 on 23 J u l y 1966, 1 on

5

September

1966,

and 1 on 3 1 ~ u l y

1968.

Four Wedge-tails banded a s a d u l t s on o t h e r i s l a n d s were c a p t u r e d a t Kure. One banded a t Kilauea P o i n t , Kauai, on

17

August 1964 was r e c a p t u r e d on 23 September 1964 and a n o t h e r one banded t h e r e on 26 March 1964 was c a p t u r e d on

5

September

1966.

Two banded a t French F r i g a t e S h o a l s , one on

8

August 1964 and one on

19

June

1966,

were r e c a p t u r e d on

19

November 1965 and 29 August

1966

r e s p e c t i v e l y .

SOOTY SHEARWATER F'uffinus g r i s e u s

The remains of e i g h t Sooty Shearwaters were found on Green I s l a n d : ¹ on

18

May

1965,

¹ on 23 A p r i l

1966,

2 on

4

May 1966, 2 on 28 May

1966,

¹ on 26 May

1968,

and

1

on 29 May 1969. F i v e of t h e s e b i r d s washed up on t h e lagoon beach and t h r e e on t h e ocean beach.

On

19

May

1966

Woodward c a p t u r e d a Sooty Shearwater w i t h ex- t r e m e l y worn f l i g h t f e a t h e r s a s it swam i n t h e lagoon.

Sooty Shearwaters a r e r e g u l a r m i g r a n t s through t h e c e n t r a l P a c i f i c .

CHRISTMAS SHEARWATER P u f f i n u s n a t i v i t a t i s

S t a t u s

Uncommon spring-summer b r e e d e r ; La. 25 p a i r s a n n u a l l y . P r e s e n t from March through October. Breeds from l a t e A p r i l u n t i l October.

Table WTS-3. Recapture rates of Wedge-tailed Shearwaters banded as adults at Xure Atoll and recaptured there (expressed as ~ercentages), 1959-6~.

Year Year Recaptured

Banded n. 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969

+

First figure represents the percentage of birds known to have been alive and the second figure is

the percentage of birds captured.

P

7

w

P o p u l a t i o n s

Robbins banded f o u r a d u l t Christmas Shearwaters and e s t i m a t e d t h e p o p u l a t i o n a s 125 i n October

1959

(Table CS-1). This r e p r e s e n t e d t h e f i r s t known r e c o r d f o r t h e a t o l l . S i n c e t h e r e was l i t t l e h a b i t a t change from 1923 t o

1959

it i s probable t h a t Wetmore overlooked t h i s s p e c i e s i n 1923. T h i s i s n o t s u r p r i s i n g , due t o t h e s m a l l p o p u l a t i o n and s e c r e t i v e n a t u r e of Christmas S h e a r w a t e r s . POBSP e s t i m a t e s a r e g i v e n i n Table CS-2.

F a i r l y a c c u r a t e p o p u l a t i o n d a t a were c o l l e c t e d f o r t h r e e y e a r s . I n 1967 f o u r n e s t s and

15

a d d i t i o n a l n e s t s i t e s were l o c a t e d , i n d i c a t - i n g a b r e e d i n g p o p u l a t i o n of a t l e a s t

38.

One y e a r l a t e r , between l a t e May and mid-August,

48

d i f f e r e n t Christmas Shearwaters, two n e s t s , and a t l e a s t 23 p o t e n t i a l n e s t s i t e s were found. I n

1969

1 2 n e s t s , 1 2 n e s t s i t e s , and 5 2 a d u l t s were l o c a t e d . Thus, i f t h i s s p e c i e s was s i m i l a r t o o t h e r p r o c e l l a r i i f o r m e s on t h e i s l a n d , t h e t o t a l p o p u l a t i o n was a t l e a s t t w i c e t h e number of p o t e n t i a l b r e e d i n g b i r d s , o r

76

i n

1967

and 1 0 0 i n

1968

and

1969.

The L i n c o l n Index can be used f o r an approximation of t h e t o t a l p o p u l a t i o n u s i n g t h e i s l a n d . Nine of t h e 42 a d u l t s banded i n

1968

were r e c a p t u r e d i n

1969.

An a d d i t i o n a l

39

a d u l t s were banded and 4 banded i n

1967

were r e c a p t u r e d . Thus,

3

⁼

-

^{42 where}

^x

⁼ t o t a l p o p u l a t i o n .

51 ^x

T h e r e f o r e , x = 238. This f i g u r e i s n o t u n r e a s o n a b l e a s almost 25 p e r c e n t of t h e e s t i m a t e d p o p u l a t i o n was handled i n both

1968

and

1969

and a con- s i d e r a b l e number of a d u l t s were unbanded i n

1969.

I n summary, t h e t o t a l Christmas Shearwater p o p u l a t i o n u s i n g t h e i s l a n d was 1 0 0 t o 200, w i t h

-

c a . 25 p a i r s b r e e d i n g a n n u a l l y .

Table CS-1. P r e v i o u s r e c o r d s of Christmas Shearwaters on Green I s l a n d , Kure A t o l l .

P o p u l a t i o n

Date of Survey E s t i m a t e Breeding S t a t u s , Remarks, References

1915

March 28

- ^-

( ~ u n t e r , 1 9 1 5 ) . 1923 A p r i l 17-22 0 (Wetmore, ms

.

⁾

.

1957 June

5 - -

( ~ e n ~ o n and Rice,

1958).

1959

October 3-8 125

4

a d u l t s banded ( ~ o b b i n s ,

1966:

5 3 ) . 1960 March 28

- -

( ~ o b b i n s ,

1966:

5 3 ) .

Table CS-1. (continued)

Population

Date of Survey Estimate Breeding Status, Remarks, References

1961 January 19-21.

0

(~obbins, 1966: 53).