Methods

As described in detail in Chapter 2, section 2.2.9, 10 chicks were selected to undergo an experimental translocation and artificial provisioning feeding trial. The oldest known chicks were selected based on wing length and their acceptance to being artificially fed with a crop tube. All 10 focal chicks were transferred to artificial burrows set up on the same island. Chicks were then provisioned on a diet of pureed Brunswick sardines, sterilised water and Mazuri seabird vitamin tablets. All chicks were weighed and wing lengths measured daily; feeding regimes were then based on daily chick weights. Chick emergence was monitored using burrow gates erected at the entrance of burrow tunnels.

In-situchicks from the focal birds’ natal colony (development test group from Chapters 3 and 4) were monitored to determine their fledging morphology (weight and wing lengths), and the feeding regimes (meal size and frequency) provided naturally by their parents. Overnight provisioning masses for in-situ chicks were quantified over their last 20 days before fledging (DBF) to reflect the same period of chick rearing as the selected feeding trial (FT) birds. Meal size calculations accounted for weight loss through respiration and excretion by adding 50% of the mean overnight weight loss from all unfed chicks to overnight weight changes of those potentially provisioned.

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5.4.0 Statistical analysis

Owing to the small sample size of FT birds (n = 9), non-parametric tests were applied in the analyses of these data. Box plots and median values with standard deviation are displayed for FT morphometric and overnight provisioning data. Mean and standard error values are also displayed for further detail and as comparative data to in-situ birds from previous chapters, which are described as parametric. Spearman Rank correlations were used to investigate the relationship between provisioning probability and overnight provisioning masses with days before fledging. The morphological variation between FT and in-situ groups at fledging for wing length and weight were tested using Mann-Whitney U tests.

Chick age is described as days before fledging (DBF). Data describing meal size,

provisioning probability and weight loss were calculated using the mean value of individual chick averages to account for variation between individuals, as per Grim (2006). The

calculation of emergence periods excluded one chick that was blocked from emerging for too long and thus the true emergence date could not be accurately determined. All analyses were conducted using Minitab 16 statistical software (Minitab Inc., 2010) and Excel 14.0

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5.5.0 Results

5.5.1 Chick selection

The wing lengths of chicks recruited into the artificial provisioning trial ranged from 88 to 119 mm, with a mean of 101.8 ± 3.8 mm (median 98.8 ± 12.2, n = 10). The weights of these selected chicks on the day of their first artificial feed at their natal site (before feeding) ranged between 37 g and 69 g, with a mean of 49.5 ± 3.0 g (median 46.5 ± 9.4, n = 10). For weight and wing lengths per chick see Appendix IV.

5.5.2 Feeding apparatus

Three available types of crop tubes were trialled:

x 10 Fg x 49 cm PVC x 10 Fg x 39 cm rubber x 14 Fg x 39 cm rubber

The larger 14 Fg rubber tube was passed into the proventriculus without complication, however on review it was considered to be too large relative to the size of the chick. Three chicks were fed once only with this tube size, of which one bird accepted the entire feed, the second had some difficulties (unsettled behaviour, spilling food, excessive vocalisation), requiring two attempts and the third chick also had difficulties, subsequently the last portion of the meal was delivered using a smaller 10 Fg PVC tube.

The 10 Fg rubber tube was too small. The internal lumen of the tube was too narrow to attach to the syringe hub after the tube length had been adjusted. Therefore this type of tube was not trialled.

The 10 Fg PVC tube was successfully used to provision chicks throughout the trial (Plate 5.1). Modifications to the tubes were however necessary, see Chapter 2, section 2.2.9.

130 5.5.3 Feeding regimes

Chicks were fed two 3.5 g introductory feeds of diluted sardine puree. At least one feed was given at their natal burrow to ensure they would accept food, and another after being

transferred to their artificial burrow. A total of 12 chicks were trial fed: one chick did not feed well with artificial provisioning and thus was not selected; a second chick that did feed well was replaced with a more suitable older chick because of its proximity to fledging. Ten chicks were inducted into the trial, and the nine chicks which fledged were artificially

provisioned for an average of 16.6 ± 0.9 days (n = 9, range: 11–20). A total of 150 collective feeds and a gross mass of 1028 ml of sardine puree were provisioned to these chicks after they were transferred to artificial burrows. After the two standard small diluted meals, chicks were fed daily with an average meal mass of 7.5 ± 0.1 ml (n = 123), ranging from 3.5 to 9 ml. A meal size of 7–8 ml per day was adequate to keep chick weight constant. Daily adjustments of 1–2 ml greater or less were allocated on an individual basis to promote weight gain or loss and achieve target fledge weights. Chick weight at the time of collection, basic provisioning information and fledging weights for all FT chicks are shown in Table 5.1. For individual chick feeding regimes and weight changes see additional data CD.

Plate 5.1 A white-faced storm petrel chick is fed a diluted version of a sardine based puree for the first time at the natal colony site. Photograph by Kay Clapperton.

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On 17.6% of feeding events chicks did not feed well (n = 38); regurgitating or seeming distressed, and requiring the feeding tube to be removed and the chicks left to settle. In such instances the feeding tube was inserted a second (76%, n = 29) or third time (21%, n = 8), and in one case a fourth time (3%, n = 1). The average number of times that individual chicks needed to be fed more than once per sitting was 4.2 ± 0.6 (median 4 ± 1.7, n = 9, range: 3–8). This is an estimated 25% of the average number of times individual chicks were provisioned artificially. Nevertheless chicks were always eventually provisioned with a suitable quantity of food.