The Titi Wainui or Fairy Prion, Pachyptila turtur (Kuhl). Part II.*Part I has appeared in Vol. 74, pp. 32–48 of the Transactions.

Transactions and Proceedings of the Royal Society of New Zealand, Volume 74, 1944-45, Page 165

The Titi Wainui or Fairy Prion, Pachyptila turtur (Kuhl). Part II.*Part I has appeared in Vol. 74, pp. 32–48 of the Transactions. By L. E. Richdale. Department of Zoology, University of Otago. [Read before the Otago Branch, September 14, 1943; received by the Editor, September 17, 1943; issued separately, September, 1944.] This paper is a continuation of the life story of the Titi Wainui as already narrated in a recent part of the Transactions. It opens with a detailed study of the chicks during their last few days ashore. Following this, appears an estimate on an important section of the community—the unemployed birds. Next are given data concerning weights and measurements of the growing chick before concluding with a section on the adults. The latter includes population statistics and a discussion of Pachyptila turtur on other breeding grounds. The Departure of the Chicks. By ascertaining the hatching and departure dates of 66 chicks I was able to work out the time they remained in the burrow. This period varied considerably from 44 to 55 days, giving an average of 49.35 days. The standard deviation is 2.81 days and the PE m .23. In the table below is shown the time ashore for the 66 chicks broken up into class intervals of 3 days with the number of chicks departing in each interval. Table XI. Time Ashore of 66 Chicks in Class Intervals of Three Days. Class Interval in Days. No. of Chicks. Class Interval in Days. No. of Chicks. 44 to 46 days 11 50 to 52 days 18 47 to 49 days 26 53 to 55 days 11 Table XII. Amount of Down Left on 66 Chicks Whose Time Ashore is Known. Amount of Down. No. of Chicks. Patches 1 Traces 7 Trace 34 1st day without down 16 2nd day without down 5 3rd day without down 1 4th day without down 1 5th day without down 0 6th day without down 1

It will be noticed from the preceding table that nearly 76 per cent of the chicks departed either with a trace of down or on the first day they were clear of all down. Generally speaking, the chicks which left early did not retain any more down than those which left late. The exception, however, was chick 9, which was the youngest to leave, being ashore only 44 days. It was the only one with patches of down when it departed. Of the five chicks which were ashore the longest period, i.e. 55 days, one had traces of down, three had a trace, and one had no down on departure. The chick which left on the 6th day after the down was gone was 54 days old. Table XIII. The Relation of the Time Ashore of 66 Chicks to the Amount of Down Left on Departure. Days Ashore Patches Traces Trace 1st day without 2nd 3rd 4th 5th 6th 44 1 45 1 1 1 46 1 6 47 5 1 1 48 1 4 2 1 49 1 5 4 1 50 1 4 3 1 1 51 4 3 52 1 53 1 1 2 1 54 1 55 1 3 1 1 7 34 16 5 1 1 0 1 The foregoing tables indicate quite plainly that the amount of down still adhering at departure may vary considerably at any given age. It was apparent, too, as the research progressed that those chicks which failed to thrive, either from lack of food or for constitutional reasons, were longer in losing their down and consequently remained ashore, on the average, for a greater period. One chick was only 45 days old when the last vestige of down had disappeared, while another took a further ten days to reach this stage. The question now arises as to whether there is a starvation period at the end of the chick's term ashore or whether the parents continue feeding to the end. In an endeavour to solve the problem I weighed a large number of chicks night and morning during their last ten days ashore with the results shown below. Table XIV. Details of Feeding of Chicks During Last 10 Days Ashore. Day Record Taken 10th 9th 8th 7th 6th 5th 4th 3rd 2nd Last No. of records 15 17 23 27 42 52 59 65 67 69 No. of times a chick unfed 3 5 6 7 10 18 26 32 50 59 % of times unfed 20 29.4 26.1 26 23.8 34.6 44.1 49.2 74.6 85.5 % of times unfed in class intervals of 2 days 25% 26% 29.8% 46.8% 80.1%

Table XV. Number of Days Each of 64 Chicks Stayed in Burrow After its Last Meal. No. of Chicks. Percentage. Fed on last night 10 15.6 Missed a meal on 1 night 12 18.75 Missed a meal on 2 nights 16 25 Missed a meal on 3 nights 14 21.85 Missed a meal on 4 nights 10 15.6 Missed a meal on 5 nights 1 1.55 Missed a meal on 6 nights 1 1.55 The above tables indicate that while 15.6% of the chicks are fed on the last night, the majority, or 81.2% miss from one to four meals immediately before they depart. It would appear that normally there is a short starvation period before the chicks leave, but in the main the drop in weight occurs gradually while the chick is still being fed. At least some of the Storm Petrel (Pelagodroma marina maoriana) and Royal Albatross (Diomedea epomophora sandfordi) parents return to the nest after the chicks have either undergone a short fast or have flown. With the Titi Wainui this procedure seems to be different for in no case were the palisades of sticks, placed across many of the burrows, knocked down after the chicks had gone. This seems to mean that in 84.4% of the cases the chicks were deliberately deserted by the parents, the former missing from one to six meals before leaving the island. Some individual records of the departure of the chicks will be of interest. Chick 3bSW, weighed on only the last six days before it left, received in food 12, 1, 8, 12, 12 and 8 grams respectively. Its age on departure was 50 days and it was free of down. Chick 29 received 18 grams on the night before it left, was unfed the second last night and received 14, 7, and 8 grams respectively for the three nights prior to that. Chick 20R was fed 7, 27 and 7 grams on the last three nights. Chick 15R was given 19 and 11 grams on the last two nights and in this case I actually caught one of the parents (recognised by its ring) just outside the burrow on the night it fed 11 grams. On the departure of this chick I placed sticks across the burrow, but no adult returned. Finally, of the 10 chicks which were fed on the last night ashore, five missed a meal on the second last night at least, one was fed on the two last nights, two on the three last, while the remaining two were fed on the last six nights to my knowledge. Prior to that I had not been weighing these two. Here are three further cases worthy of mention. Chick 1bNW, though not fed on the last two nights received the huge total of 54 grams on the third last night. Chick 49R in the last four nights received 13, 26, 31 grams and then was unfed, while chick 22 on the last seven nights was fed 33, 51, 17, 4, 0 grams, before being left unfed on the final two nights. I have gained the impression that the chicks resemble the Storm Petrels in that they do not come to the mouth of the burrow till either the night they go or the night before. Once having emerged from the burrow they do not appear to return as seems to be the procedure with the Mutton-bird (Puffinus griseus) chicks. At nest

3R on February 12, 1942, the chick was observed just behind the palisade of sticks across the burrow entrance. Next morning the sticks were still intact so that the chick had not been outside nor had it been fed. That night at 11 o'clock I saw it emerging through the sticks, but when my torch shone on it the light caused it to return to the burrow. I was fortunate in witnessing the departure of Chick 5. At 9.30 p.m. on February 16, before complete darkness, I arrived to find the chick just out of the burrow entrance. In a few minutes it was on the edge of the cliff only a few feet away and as far as I could tell took off. It may have fallen on to lower ground but a search failed to reveal it. When the chicks do decide to leave many of them issue forth long before it is properly dark and a considerable tune before any adults have appeared over the island. Frequently, in this semi-darkness, they hit the tent indicating that they had been attempting to fly. Many were found clambering up to the top of the Muehlenbeckia round the tent and others were running at considerable speed along the paths. Moreover, they do not seem to be deterred by moonlight nights or by rough weather, behaviour which is in great contrast to that of unemployed adults. One chick, on February 8, was found to have left the burrow. That night I discovered it sitting in the sedge not far away, having apparently spent the day somewhere else. This incident indicates, too, that all chicks do not leave the island on the night they emerge from the burrow. Chicks without down are not easily distinguishable from the adults, but the careful observation of the ridge before the nostril and the whitish edging to the tips of the scapulars will indicate a fledgling. Table XVI. Average Weight of 62 Titi Wainui Chicks During Their Last 8 Days in the Burrow. Day Before Leaving Weight in gms. Day Before Leaving Weight in gms. 8th 148.7 4th 133.3 7th 147.8 3rd 127.5 6th 143.5 2nd 120 5th 140.5 Last 112.1 The weight on the 8th day before departure varied from 104 to 190 grams while on the last day it was from 90 to 131 grams. The 190-gram chick on the 8th last day left when weighing 131 grams, being the heaviest of all the 62 chicks. The chick weighing 104 grams on the 8th last day left at 95 grams and had throughout never been very heavy. The above table indicates a gradual falling off in weight during the last eight days but as I mentioned previously this does not mean that feeding had ceased. Actually some of the chicks were fed on the last night in the burrow. From the table below it will be observed that nearly 70% of the chicks set out between the weights of 105 and 124.9 grams.

Table XVII. Departure Weights of 65 Chicks in Class Intervals of 10 Grams. Class Interval in Grams. Frequency. Percentage. 125 to 134.9 6 9.3 115 to 124.9 22 33.8 105 to 114.9 23 35.4 95 to 104.9 13 20 85 to 94.9 1 1.5 Comparing the weight of the chicks when they leave the burrow with that of the adults caught at night just as they reach the island, it will be found that the chicks, on the average, are considerably lighter. This is in marked contrast to the Storm Petrel chicks, which, at the time of leaving the burrow are heavier than the adults. The weight of the Titi Wainui adults given in the following table may be a little higher than normal, as when caught they had in some cases not fed the chick. Table XVIII. A Comparison of the Weights of 100 Parents Caught on Whero at Night as They Arrived With 62 Chicks on the Night Each Left the Burrow. Type of Bird Average gms. 6 gms. PEm Range gms. Adult 131.8 13.75 .92 100 to 162 Chick 112.74 9.1 .77 90 to 131 Difference 19.06 ±1.2 In order to ascertain the growth of the wing and its length on the day of departure a number of chicks were measured daily during the last ten days in the burrow. The results are given in the table below. Table XIX. Increase of Growth of Wing of 16 Titi Wainui Chicks During Last 10 Days in Burrow, Divided into 2-day Class Intervals. Class Interval In Days Before Leaving Average 10th and 9th 153.1 mm. 8th and 7th 159 mm. 6th and 5th 163.7 mm. 4th and 3rd 168.8 mm. 2nd and last 173.5 mm. As the increase in growth from day to day was slight, owing to the liability to small errors in measurement, especially upon live birds, it was thought desirable to group the measurements into class intervals of two days. The variation in length for the last day ranges from 165 to 180 mm. The chicks measured for the purpose of the above table were different from those used for table XXIV.

In the following table the wing of 26 Titi Wainui chicks is compared with 100 parents, 50 of each sex, being taken from the breeding burrows on Whero during the 1941–42 season. From the results which indicate a significant difference, it would appear that the chicks do not attain their full wing length till they have left the burrow. Table XX. A Comparison of the Wing Measurements of 26 Titi Wainui Chicks the Day Each Left the Burrow with 100 Parents, 50 of Each Sex, Taken on Whero in the 1941–42 Season. Type of Bird Average mm. 6 mm. PEm Range mm. Adult 182.45 3.43 .22 170 to 191 Chick 175.11 4.18 .54 168 to 180 Difference 7.34 ±.59 On February 5, 1942, the first of the chicks under observation left its burrow. None departed on the 6th, while on the 7th, two set out. Altogether 73 left from burrows under observation while 42 were found on the surface of the ground after they had left a burrow which I had not found. On February 28, after a period of 23 days the last chick left so that the departure period is relatively short. In the table below the departure dates are grouped into class intervals of 3 days each. Chicks under observation and chicks caught on the surface are given separately. It will be noted, too, that the bulk of the departures, i.e. 84%, occur between February 8 and 19. Table XXI. Departure Dates of 115 Titi Wainui Chicks Placed in Class Intervals of 3 Days. Dates of Class Intervals Chicks In Burrows Under Observation Chicks Found On Surface After Leaving Burrows Total Feb. 5 to Feb. 7 3 3 Feb. 8 to Feb. 10 11 2 13 Feb. 11 to Feb. 13 13 6 19 Feb. 14 to Feb. 16 22 15 37 Feb. 17 to Feb. 19 15 13 28 Feb. 20 to Feb. 22 3 4 7 Feb. 23 to Feb. 25 5 1 6 Feb. 26 to Feb. 28 1 1 2 73 42 115 The Effect of the Moon. The effect of the moon on the Titi Wainuis is interesting and will be studied from two angles. In the first instance I shall make records concerning its effect on adults feeding their young, and in the second, its influence on the behaviour of the unemployed population.

In table XXII below my time on the island in both seasons is divided into 5-day intervals, using as the key period that beginning a day before the full moon and ending four days later. This was the period yielding the maximum amount of moonlight in midsummer. The number of times chicks could have been fed coincides with the number of times weighed each morning. The number of times fed indicates the number of times the morning weight was greater than the previous evening. Those occasions when the chicks were not fed after their last meal ashore are not counted as I consider that this lack of meals occurs whatever the state of the moon. The purpose of the table is to discover the effect of the moon when the parents are actually feeding, not when they have stopped. Table XXII. Effect of the Moon on the Feeding of Chicks. The Key 5-Day Intervals Include the Day of the Full Moon. Class Interval 1940–41 State of Moon No. of Times Chick Could Have Been Fed No. of Times Fed Per-centage Dec. 23 to Dec. 27 7 4 57 Dec. 28 to Jan. 1 31 Dec., New moon 26 21 81 Jan. 2 to Jan. 6 35 30 86 Jan. 7 to Jan. 11 35 27 77 Jan. 12 to Jan. 16 13 Jan., Full moon 35 34 97 Jan. 17 to Jan. 21 36 32 89 Jan. 22 to Jan. 26 40 28 70 Jan. 27 to Jan. 30* Last day chicks weighed. 28 Jan., New moon 32 26 73 1941–42 Jan. 22 to Jan. 26 17 Jan., New moon 8 7 87.5 Jan. 27 to Jan. 30 50 38 76 Jan. 31 to Feb. 4 1 Feb., Full moon 52 46 88.5 Feb. 5 to Feb. 9 83 61 73.5 Feb. 10 to Feb. 14 114 91 79.8 Feb. 15 to Feb. 19 16 Feb., New moon 50 38 76 Feb. 20 to Feb. 24 23 18 78.3 From the preceding table it would appear that generally speaking breeding adults return to feed their chicks irrespective of the state of the moon. In fact, during the interval containing the full moon, in each season, a higher percentage of chicks was fed than on darker nights. With the Storm Petrels during this same period the position was reversed for in 1940–41 only 23% were fed during January 12 and 16, and in 1941–42 73% from January 2 to 6, 66% from January 31 to February 4, and 55% from March 2 to 6. All these periods contained the full moon and the number of chicks fed was relatively low. Of the two full moon intervals under consideration for Titi Wainuis the period from January 12 to 16, 1941, was easily the brightest, the interval in 1942 being quite cloudy with little direct moonlight. In spite of the light the first interval yielded the highest return of chicks fed, for out of a possible of 35 meals only one was missed, that one occurring on January 15. The meals ranged from 3 to 45½ grams but most of them were very moderate, 83% being under 20 grams.

On any ordinary dark night during the latter half of December, 1940, the Titi Wainuis were very numerous and their cries dominated the night noises till daylight. The same position applied both in 1938 and in 1941. By January 9, 1941, the moon was far enough advanced to show a bright light at 10.30 p.m. resulting in there being very few birds about. Five of the seven chicks under observation were not visited while one of the two fed received only a small meal, so that I began to form the impression that the parents stayed away. On the 10th all chicks were fed with large meals ranging from 14 to 32½ grams. Up till midnight it was fairly light but later it became overcast. On January 11 the moon was bright up to 2 a.m. before the clouds obscured it, and on this occasion three of the chicks were not fed. Then followed the 5-day full moon interval during which all chicks, except on one occasion, were fed. On January 23, 1941, a dark night, only two of eight chicks being weighed were fed and these received 40 and 26 grams respectively. This night coupled with January 9 previously, a moonlight night, gives the lowest record that season for food transmitted in a single night. Hence there must be other factors apart from the moonlight that prevent feeding. On January 25, 1941, a heavy fog developed at 11 p.m. Three of the eight chicks were not fed while the others received 4, 5, 6, 8 and 30 grams respectively. Perhaps those parents which did not reach the island before 11 p.m. had to stay away, while the four light meals would seem to indicate that only one parent fed at those particular nests. In 1941–42, 10 chicks were weighed during the period from January 26 to February 28, at which date the last had flown. Only twice were as many as three chicks left unfed, while on all the other nights the number not fed was less than three. It will be noted that the number of chicks fed during each 5-day interval was comparatively even. To sum up, it would seem that feeding proceeds as usual during moonlight nights. As against this, Titi Wainuis are rarely seen and never heard on moonlight nights. It follows therefore from table XXII that feeding adults which arrive at the burrow without much preliminary circling and calling, are unnoticed. I firmly believe, too, supported by the witnessing of the arrival of breeding birds that this is the usual procedure of this type of bird irrespective of the condition of the night. Seemingly, they have an important mission in life and no time for other activities. Similar behaviour is exhibited by breeding Royal Albatrosses, which, when the owners of a nest, neither circle unnecessarily nor dally prior to landing. Unemployed Birds. During January, 1941, I noticed fewer Titi Wainuis in the air at night, and this diminution in numbers was especially marked after the moon early in the month. The same condition prevailed in January, 1942, when on the 16th of the month I observed that the numbers of this species had suddenly decreased. Full moon occurred on January 3. The procedure seems to be that after the moon early in January or perhaps late December, the island is inhabited largely only by birds feeding chicks, or, in other words, most of the unemployed birds have left the island for that year.

As already mentioned, when I reached the island in all three years, 1938, 1940 and 1941, just before Christmas, Titi Wainuis were very plentiful. So persistent and raucous was the calling from numerous throats that complete sleep was, for some nights, impossible. As January advanced these calls slowly diminished in intensity. I am of the opinion that these noisy chatterings came not from the breeding birds, which, I believe, after some brief hovering, landed, entered their burrows and relieved their mates, but from the throats of the unemployed population. It would appear then that the large numbers of Titi Wainuis circling and calling out on ordinary dark nights are unemployed birds still on the breeding grounds. If this surmise is correct the proportion of unemployed to breeding birds must be high. During the early part of my visit from about December 20 to early January, Titi Wainuis were present in the burrows in the day time either in pairs or singly. At night a considerable amount of excavating and entering of occupied and unoccupied burrows took place, scant courtesy in this connection being shown at times to the rights of the smaller petrels. I have several records where Storm Petrels lost either their eggs or their chicks because of these vagabond Titi Wainuis. Between December 29, 1941 and January 25, 1942, I have recorded eight cases. On five occasions the egg had been scraped out, and on two occasions a young chick was ejected. One of these was dead, the other I removed and placed under a foster parent which had that night lost its egg because of a Titi Wainui. In the eighth case a chick, 32 days old was ejected and although I did not find it again I scarcely think it could have perished. Moreover, of the 33 Storm Petrel chicks under observation in 1940–41, no less than six burrows were usurped by Titi Wainuis. Four of these contained a breeding pair of Titi Wainuis while two others were occupied by unemployed birds. Neither do the Kuakas (Pelecanoides urinatrix) escape interference from these Prions. I had occasion once to take a breeding Kuaka to the tent for measuring and on returning it to the burrow I found a Titi Wainui in the burrow with the Kuaka chick. So far, I have no evidence, however, of Titi Wainuis ousting Kuakas which are in occupation or of a chick being scraped out. Kuaka chicks, of course, are guarded all the time by their parents till they are about 12 days old. Of 18 pairs of Kuakas marked in burrows in 1940–41, three pairs had their homes occupied by Titi Wainuis. Two other pairs occupied an old Kuaka nest where only one bird had been ringed, while two more pairs of Titi Wainuis were in holes previously used as subsidiary burrows by Kuakas. In yet another case, in 1941–42, a Titi Wainui was incubating an egg while embedded in the floor of the nest was an old Kuaka egg. Of course, it is not known for sure whether the original Kaukas had been ejected from their home. These activities have contributed to my impression that Titi Wainuis are increasing in numbers.

There was no evidence that Titi Wainuis had been ousted from their burrows by Pararas (Pachyptila vittata). Where the former nested in the Mutton-bird area, however, considerable ejection had occurred. In its turn the Titi Wainui has to give way to the Mutton-bird which scrapes out any species which happens to be in its path. In 1942–43, I found a Titi Wainui sitting on an egg in an old Mutton-bird burrow which was occupied by the latter species in the previous season. Incubation continued until the end of December when I found the egg, on the verge of hatching scraped out into the night—an unemployed Mutton-bird had decided to take up residence. This was by no means an uncommon occurrence in the western sedge area. An interesting case of a pair of unemployed birds occurred at nest 47 in 1940–41. On December 24 a nest was found with a single bird which was ringed. For the next two days there was no bird but on the 27th an unringed bird was present, which I took the occasion to ring. No further sign appeared till the 31st when slight excavations indicated that at least one bird had been home at night. Across the entrance to the burrow I erected sticks but no further sign of occupation occurred that season. Now, in both 1941–42 and in 1942–43, these birds returned to this burrow and succeeded in rearing a chick. It has occurred to me that this species may indulge in a year's preliminary courtship prior to the laying of eggs as seems to be the behaviour with the Royal Albatross. Weights and Measurements of the Growing Chick. In Table XXIII below are given the 9 a.m. and 9 p.m. weights of 17 chicks during part of their life in the burrow. The weights of seven chicks up to 28 days of age were taken in 1940–41 and are given first, followed by those for other chicks taken in 1941–42 from 29 days old till they flew. In working out the data for the table all the weights concerned were put down in columns, one for each day. The columns were then divided into class intervals of four days, each column being then added up and averaged. These four averages were then averaged giving the average for each four day interval. In this way any tendency for extreme low or high individual weights was smoothed out. Each class interval therefore represents an average of many cases as indicated in columns 2 and 4. The last two intervals involve only a very few cases because some of the chicks had departed. It will be noticed that between the two sections of the table there is a big difference in weight. This is due to the fact that in 1940–41 two of the chicks being weighed, though healthy, were much lighter than average chicks. Even so there is a general increase in weight up to the 41–44 day interval after which there is rapid decline, for some of the chicks begin to fly in the next interval while the bulk go between the 49–52 day period. The quantity of food given on the average per meal after the 41–44 day interval is distinctly less.

When the weights of 62 chicks (table XVI) were put down and averaged for their last eight days ashore there was shown to be a steady fall in weight. Table XVII indicates that nearly 70% of the chicks leave weighing between 105 and 124.9 grams. To sum up, it would appear that the chicks retain a comparatively heavy weight to within about four days of departing when many of them drop considerably during a short fast period of varying length, even up to six days in extreme cases. As against this 15.6% of the chicks were fed on the night before they left. Table XXIII. 9 a.m. and 9 p.m. Weights of 7 Chicks to 28 Days of Age and then 10 Chicks Till They Flew, Grouped into Class Intervals of 4 Days. Class Interval in Days 1940–41 No. of wts. a.m. wts. gms. No. of wts. p.m. wts. gms. Difference between even, and morn. wts. 1–4 17 21.76 19 20.86 .9 5–8 28 34.2 28 29.8 4.4 9–12 28 52.44 28 44.48 7.96 13–16 28 65.13 28 55.26 9.87 17–20 28 78.86 28 70.61 8.25 21–24 28 96.79 28 88.08 8.71 25–28 28 104.35 28 97.64 6.71 1941–42 29–32 26 156.43 31 144.3 12.13 33–36 36 157.93 38 149.34 8.59 37–40 40 168.2 40 155.25 12.97 41–44 40 166.72 40 154.52 12.2 45–48 37 147.6 37 138.98 8.62 49–52 17 127.02 17 121.56 5.46 53–56 3 124.66 3 118.66 6.0 Some of the weights and increases in weights of the 10 chicks which were weighed in 1941–42 from 28 days of age are interesting. Four of them passed the 200-gram mark. One did so on one occasion only, two did it three times and one exceeded this weight four times. Chick 3R was 225 grams at 9 a.m. when 39 days old and left the island eight days later weighing 131 grams at 9 p.m. (see Graph). Actually chick 5 was the lightest, reaching a peak weight of only 148 grams at 9 a.m. when 34 days old; its final weight was 98 grams when 49 days old. This was the only one of the ten chicks to fly under 100 grams, the range being from 131 to 98. The graph gives a good idea of the growth curve of a chick and also clearly shows the peaks and hollows caused by the irregular amount of food received, and by the weights when no feeding occurred. The 9 a.m. and 9 p.m. weights of three typical chicks are recorded. Those for chick 22 are complete up to the 39th day and indicate a greater number of nightly fasts than usual. The graph for chick 7R overlaps that for chick 22 and is inserted to indicate what happens during the final stages. This chick stayed ashore much longer than the average and did not attain a very heavy weight. Chick 3R was one of several, which besides being heavier in its earlier stages, reached a very heavy weight not long

before departure. In the two last chicks the method of attaining flying weight and the extent of the “starvation period” are clearly shown. In the table below is given a summary of the weekly average measurements and weights of 10 Titi Wainui chicks from the day of hatching to their final days ashore in 1941–42. Table XXIV. Average Weekly Measurements and Weights of 10 Titi Wainui Chicks. Feature 1st day 8th 15th 22nd 29th 36th 43rd 50th Bill 12.33 14.33 15.96 17.92 19.65 20.94 21.62 21.77 Width 6.94 7.67 8.46 9.46 9.58 10.06 10.35 10.5 Depth 6.97 7.37 7.5 7.62 Wing 16.66 19.67 27.5 54.16 102 130.1 157.2 174.5 Tail 1.125 10 25.5 47.3 69.8 84.6 Toe and claw 16.08 19.04 24.79 30.21 35.85 38.33 38.77 38.77 Claw 3.29 3.88 4.29 5 5.72 6.3 6.45 6.45 Weight at 9 p.m. (gms.) 20.08* The 9 p.m. weights are influenced by meals during the day in some cases. 38.1 66.83 88.86 129 148.5 151 118.2 In order to find out if the bill of the fully fledged chick is smaller than that of the adult I measured the length, width and depth of 100 chicks and compared them with a 100 parents, 50 of each sex. The results are shown statistically in table XXXV below. Before allowing that a difference between means is significant I have followed the ruling that it must be at least four times the value of the probable error of the difference. Applying this rule, the difference in depth is not significant, in length it is significant but not to any great extent, especially when the range is considered. In width, however, the difference is greater and is also apparent in the range. Even so these slight differences are not noticeable to the eye as is the case with adult and fledgling Storm Petrels. Certainly the difference is not as great as has been supposed and in considering this statement the weekly growth records given in table XXIV should be consulted. Falla has shown (1940, pp. 219–220) that the width of the bill in fledgling Prions shrinks considerably after it has been dried, thereby explaining the small bill widths of some of the published measurements. Table XXV. A Comparison of the Bill Measurements of 100 Fully-fledged Chicks with 100 Parents, 50 of each Sex, all Taken on Whero in 1941–42. Type of Bird Bill Mean mm. 6 mm. PEm Range mm. Adult Length 22.11 .79 .05 20 to 24 Width 10.88 .4 .025 10 to 12 Depth 7.23 .28 .02 6 to 8½ Chick Length 21.66 .8 .05 20 to 24¼ Width 10.33 .41 .03 9¼ to 11 Depth 7.34 .39 .026 6 to 8 Difference Length .45 ±.07 Width .55 ±.04 Depth .11 ±.03

The Adults. Already the reader will have gleaned a certain amount of information concerning the behaviour of the adults. Far greater irregularity in its habits distinguishes its behaviour from that of the Kuakas while compared with the Storm Petrel it is not quite so irregular. Rarely is the egg left cold as is the case with the Storm Petrel. The periodic span of incubation by each parent Titi Wainui is often longer than in the Storm Petrel while in the Kuaka the change of guard occurs daily. Though the chick is left alone very soon after it is hatched it does not experience the long fast periods endured by some of the Storm Petrel chicks. Moonlight nights do not influence the homecoming of the Titi Wainui parents to the same extent as the Storm Petrel parents, while the Kuakas are not affected at all. Unlike the Storm Petrels both the Titi Wainuis and the Kuakas are seen off-shore in the daytime during rough weather. When handled, the adults are usually very noisy, uttering harsh cries and then often subsiding to canary-like calls. Possessing the potoer of biting quite ferociously they can inflict considerable pain when the point of the bill is inserted repeatedly in the same spot. Many of them when caught, and even when pulled out of the burrows in the daytime if they are attending chicks, cough up a quantity of food. When the hand is inserted into the burrow it is usually severely bitten by most birds. The call of the Kuaka is a distinctive one, easily recognised, but with the Titi Wainui the calls are so many and diverse that I have not yet defined them all. Moreover, the presence of hundreds of Storm Petrels adds to the confusion and I am convinced that some of the calls of each species are very similar. The loud “Poor popper” and “Popper, popper, pop”, as described in my Whero paper (1942, p. 93) are easily distinguished. Then there is the beautiful canary-like call uttered by both chicks and adults; the chicks as they get older will emit the “Poor popper” cry. The oldest in 1940–41 when playing with me would bite my hand, at the same time creating a comical situation with the incessant “Poor popper” cry. Some harsh cries, too, were uttered by the adults but I have not yet been able to enumerate them. Table XXVI. Population Statistics of Titi Wainuis on Whero, 1940–41 to 1941–42. Description of Birds. 1940–41 1941–42 Breeding birds ringed 63 94 Breeding Birds not ringed 25 46 Other birds ringed 19 8 Birds which deserted eggs 24 22 Parents of unrecorded chicks 14 10 Unringed parents of chicks found on surface 84 145 264 Chicks marked in burrow 29 73 Chicks marked on surface 42 29 115

In the above table “breeding birds ringed” means those parents actually found in charge of a burrow on any part of the island. Some of the parents were not caught while in other cases the egg was deserted or some mishap overtook the chick before the adult could be ringed; this class is therefore called “breeding birds not ringed.” Stray birds picked up on the surface and whose breeding status was unknown are classified as “other birds ringed.” Wherever deserted eggs were found it was assumed that two birds were concerned and these are described as “birds with deserted eggs.” “Parents of unrecorded chicks” belong to those chicks in burrows which for some reason were not recorded. In 1941–42, 42 chicks were picked up on the surface at night after they had left the burrow, and hence the class of parent “unringed parents found on surface.” It is interesting to review the Titi Wainui population of 400 as stated in my Whero paper (1942, p. 91). This is obviously far too small a number. Burrows are numerous in the western sedge area, more particularly in the northern end. In the sedge on top of the island and round the cliff edges they are also just as plentiful. Most of the chicks caught on the surface were taken in the Muehlenbeckia, and this fact coupled with the deafening noise that proceeds from the area early in the season produces sufficient evidence that the Muehlenibeckia is the dwelling place of many birds which were not found. Searching in the areas mentioned above did not yield success as the burrows in the sedge fell in easily and those in the Muehlenbeckia were inaccessible. Taking into consideration all the factors concerned I should say that the Titi Wainui population of Whero is at least 800 birds. Arriving on the island, as I did, rather late in the Titi Wainui season I probably have not a thorough conception of the unemployed population which may be numerically greater. If so, the figure given above will be far too low. As already indicated, the Skua (Catharacta skua lonnbergi) attacks and devours the Titi Wainui, but during my several sojourns, very seldom, to my knowledge, has a bird been captured on the island. I have records of two small chicks in 1940–41 and one in 1938–9 being taken. Of course, the remains of this species are plentiful in the middens but most of these must represent victims caught at sea. Already, I have discovered in these middens four sets of remains of two different species of petrels, which are not found on Whero. The intriguing question of the domestic arrangements of individual birds and pairs from season to season will be reserved for a supplementary paper, by which time a considerable amount of data will be available. For the present it will be sufficient to say that from the experience of three consecutive seasons there is a tendency for the birds to pair up in the same burrow. There are, however, some pairs which have shifted to a neighbouring burrow, and also single birds which have been found in the same burrow with an unmarked and presumably a new mate. Some of these

single birds have been discovered in another burrow with a new mate, while the old burrow has been occupied by other birds. Above all, there is one case, and this is the first I have proved in the petrel world, of a “divorce.” By that, I mean, I have located a bird with a new mate in possession of an egg, and only a few feet away is its previous season's mate, also with a fresh partner and incubating. There is every evidence to support the fact, too, as in the case of the Mutton-bird, Storm Petrel and Kuaka, that the Titi Wainui returns to the same part of the island when on land. A unique event occurred on December 31, 1940, when I found two birds in a burrow with an egg. The one incubating coughed up food and weighed 143 grams so it had evidently changed guard the night before; the second bird weighed 109 grams, but did not cough food. This marks the only occasion I have found two birds with an egg in the daytime. Generally speaking, in the daytime, adult birds are not to be seen near the island, though on odd days, especially after rough weather, it is possible that they may be observed with the naked eye flying over the waves. On January 30, 1941, however, the appointed day for my departure from the island, the worst storm I experienced arose. Being storm-bound, I took the opportunity to watch the birds off-shore, and I noticed that all day Mutton-birds, Kuakas and Titi Wainuis were very numerous round the island; Kuakas and Mutton-birds had frequently been seen before. The Titi Wainuis were very close in and the Skuas, though sitting on the rocks watching them, made no attempt to attack. Evidently, the gale was a sufficient deterrent. The Titi Wainuis fed by submerging altogether or by “standing” on the water and ducking the head in, while sometimes they rested on the water and submerged the head. This habit of “standing” on the water seems to explain the presence of a ring of seaweed round the legs of the birds when they are handled on shore. Very little hydroplaning with wings out was noted, though sometimes one bird would proceed in this fashion for about a foot. Table XXVII. Measurements and Weights of 100 Breeding Titi Wainuis, 50 of Each Sex, Taken on Whero in 1941–42. Feature Mean mm. 6 mm. PBm Range mm. Bill   Length 22.11 .79 .05 20 to 24   Width 10.88 .4 .025 10 to 12   Depth 7.23 .28 .02 6 to 8.5 Wing 182.5 3.43 .22 175 to 191 Tail 91.69 2.93 .19 86 to 98 Toe and claw 40.4 1.6 .1 35 to 45 Claw 7.23 .64 .04 5¾ to 9 gms. gms. gms. Weight 131.8 13.75 .92 100 to 162

Table XXVIII. Measurements of 14 Birds Taken on the Poor Knights, November, 1940. Feature Mean mm. 6 mm. PEm Range mm. Bill   Length 23.36 .76 .14 22½ to 25½   Width 11.75 .46 .08 11 to 12½ Wing 183.86 4.86 .9 171 to 190 Tail 89.57 3.06 .57 82 to 94 Toe 40 1.22 .23 38½ to 42 Table XXIX. The Difference Statistically Between Whero and Poor Knights Birds. Bill Length Width Wing Tail Toe Difference in mm. 1.25 .87 1.43 2.12 .4 PEd .15 .08 .93 .6 .39 From data given in the three above tables it is possible to compare the Whero birds with 14 of those measured on the Poor Knights off the east coast of North Auckland. The measurements are given by Buddle (1941, p. 60). The difference in the two sets in wing, tail and toe is not significant. In the length and width of the bill, however, the Poor Knights birds are significantly larger than those from Whero. Falla (1940, pp. 229–231) believes that the turtur assemblage may be divisible into two groups, a small-billed type from Stewart Island, from a point west of Australia, and still present in the Chatham Islands population, and a robust-billed type north of these areas including Bass Strait. The figures from the Poor Knights would seem to support these contentions. Those given in table XXX even though some of the averages are greater than those in table XXVII, indicate that the range in all cases falls within the range of birds handled on Whero. It would be interesting to have a large series of measurements from birds of the more northerly breeding areas. It should be recalled as stated further back that turtur on the Poor Knights breeds much earlier than the type on Whero. Literature Cited. Buddle, G. A., 1941. Birds of the Poor Knights. The Emu, vol. xli, pp. 56–68. Falla, R. A., 1940. The Genus Pachyptila Illiger. The Emu, vol. xl, pp. 218–230. Fleming, C. A., 1939. Birds of the Chatham Islands. The Emu, vol. xxxviii, pp. 380–413 and 492–509. Murphy, R. C., 1936. The Oceanic Birds of South America, vol. i, New York. Richdale, L. E., 1942. Whero: Island Home of Petrels and Other Birds. The Emu, vol. xlii, pp. 85–105. Wood Jones, F., 1937. The Breeding of Prions on Islands off the Coast of Victoria. The Emu, vol. xxxvi, pp. 186–188.

The graph for Chick 22 ends on the 39th day; that for Chick 7R begins on the 36th day. 9 a.m. and 9 p.m. weight of three Titi Wain clicks during a portion of their life in the burrow.

Fig 1 Titi Wainui Chick 40 Days Old 20/1/41 Fig 2 Another Chick 46 Days Old 12/2/42 Note rapid disappearance of down at this stage.

Table XXX. Measurements of Pachyptila turtur given by Other Observers. Authority Locality No. of Cases Bill Width Depth Wing Tail Tarsus Toe Murphy At sea off N. end of N.Z. 10 21.8–24.2 10–11.8 174–187 81.5–93.4 29.4–31.9 35–39.3 (1936, p. 631) (23.3) (10.9) (180.3) (85.7) (30.7) 36.7) Falla Chatham Island 4 21–23 10–11.2 169–178 85–92 29–30 36–39 (1940, p. 230) (22) (10.8) (173.8) (90) (29.8) (37) Motunau Island 3 21–23 10.7–11 182–185 90–94 31–32 38–42 (22.3) (10.9) (183.3) (92) (31.3) (40.7) Jacques Lees 4 21–23 9.8–10 175–178 85–90 30–31 36–39 (21.8) (10) (176.3) (87) (30.3) (37.3) Bench Island 9 20–22.5 10.75–12 174–185 (21.8) (11.3) (179.3) Fleming Chatham Island 5 23 10–11 6.5–7 172–182 80–88 28–30 35–38 (1939, p. 400) (10.8) (6.9) (177) (85) (28.7) (37) Wood Jones Lady Julia Percy Island 8 23–24 10.5–11 165–174 30–32 (1937, pp. 187–8) (23.1) (10.8) (170.3) (31.5) Lawrence Rocks 2 22–23 10–10.5 169–171 31–32