ANALISIS Y DISCUSIÓN

For those predator species for which Standard Methods have been devised, each parameter is detailed in a separate method. A typical Standard Method sheet features:

SPECIES: the name of the indicator species

PARAMETERS: simple statement of what is being measured

ASSOCIATED PARAMETERS: parameters related to that which is being measured

AIM: a restatement in greater detail of the parameter being measured . DATA COLLECTION:

GENERAL PROCEDURE: sets out in cookbook form step-by-step

instructions e.g. size of sample, frequency of observations, what to record. MANDATORY DATA: basic minimum data to be recorded.

HIGHLY DESIRABLE DATA: additional data which help in interpretation of observations

PROBLEMS TO BE CONSIDERED: practical tips on minimising error e.g, due to equipment failure, human interference

DATA PROCESSING AND ANALYSIS gives detailed instructions on how the data obtained should be analysed.

INTERPRETATION OF RESULTS: the meaning of the results obtained from processing the raw data.

REFERENCES

5.8.2 Standard Methods i n use i n 1 995

Penguins

Penguin species monitored are Adelie, Gentoo, Chinstrap, and Macaroni, but Adelie penguins are the only species to which all methods in current use are applicable, as indicated in the table below.

Method Species Parameter Sites

Al Adelie (A) Adult weight on first Prydz Bay (A) Chinstrap (C) arrival at colony S. Orkney (A, C)

Macaroni (M) S. Georgia (M)

S. Shetland (A, C) A2 Adelie Chinstrap Duration first Prydz Bay (A)

incubation shift of both S. Orkney (A, C) members of breeding

pair

A3 Adelie , Chinstrap Breeding population Prydz Bay (A) Gentoo (G) Macaroni size S. Orkney (A, C)

S. Georgia (G, M)

S. Shetland (A, C, G, M) A4 Adelie , Chinstrap Annual survival Prydz Bay (A)

Gentoo Macaroni S. Orkney (A, C)

S. Georgia (M, C, G) S. Shetland (A, C, G, M) AS Adelie Chinstrap Duration of foraging Prydz Bay (A)

Macaroni trips S. Orkney (A, C)

S. Georgia (M, C, G)

S. Shetland (A, C, G, M) A6 Adelie Chinstrap Breeding success Prydz Bay (A)

Gentoo Macaroni S. Orkney (A, C) S. Georgia (M, C, G) A7 Adelie Chinstrap, Chick weight at Prydz Bay (A)

Gentoo Macaroni fledging S. Orkney (A, C) S. Georgia (M, C, G) S. Shetland (A, C, G, M) AS Adelie Chinstrap Chick diet

Macaroni

A9 Adelie Chinstrap Breeding chronology Prydz Bay (A)

Gentoo Macaroni S. Orkney (A, C)

5.8.3 Sta ndard Methods considered in detail

Where possible, the views of field scientists were ascertained for this section.

A: Penguins

With a few exceptions, the Methods do not appear to give any insight into the performance of the penguins beyond the current season: performance in following seasons cannot be predicted. Exceptions are Methods A3 and A4, which, when applied over the long term, could allow interannual

comparisons and trends to be related to environmental factors. Fledging success may give clues to the possible increase or decrease of the breeding population in succeeding seasons. The main limiting factor to breeding success appears to be the availability of food during the chick rearing period, particularly the guard phase, when chicks are young. The distance adult birds have to travel appears to be critical also during this phase (Clarke pers. comm.).

Most field scientists contacted agree that the Standard Methods are

effective in obtaining the information needed for the chosen parameters. They feel more emphasis needs to _be placed on obtaining weather and climate data, particularly sea ice extent and distribution, as well as the locations of polynyas. Clarke (pers. comm.) states:

We need to gain a better understanding of how the whole ecosystem works: how ice, currents, winds and weather interact with the krill population density, distribution and breeding, and how all this affects the penguins. We also need to investigate what things other than food availability affect

penguin breeding success: snow cover on nest sites, ice extent, disease so that the effects of these can be differentiated from the effects of krill availability. A tall order!

Al Adult on arrival at

This parameter aimed at obtaining the mean weight of adult birds at their first arrival after winter. The date of arrival is of importance. If this is the same every year, this means that the cycle is governed by some external signal, for example, hours of daylight. If the date varies but penguins arrive at the same average weight from year to year, it means that there is

breeding can commence. It would be valuable if individual birds could be identified and their weight and dates of arrival mapped over a number of years. The method further specifies that data should be analysed

separately for males and females, as their weights as well as patterns of behaviour can vary according to gender. Times of arrival and body condition may yield qualitative information about food availability and the distance between the colony and open water but definite conclusions cannot be drawn without further information. The size of birds is also influenced by the gender and age of birds.

It is difficult to see how this parameter can give information specific enough to yield management advice; it needs to be viewed in the context of other variables. It gives an indication of the state of the marine

environment in the area where the birds overwinter - late arrivals may suggest a paucity of food or unfavourable conditions for obtaining it. The first edition of this method required capturing and manual weighing of large numbers of birds in the study colony at frequent intervals over the arrival period.

A2 Duration of first incubation shift

This method records the time spent incubating eggs by each member of a breeding pair. It is an indirect indicator of food availability, as a readily available food supply to the feeding bird would possibly result in a more timely relief of the incubating bird. The condition of the birds prior to breeding and their experience as breeders affect the time spent foraging. In years of adequate food supply, most of the birds undertaking the first incubation shift of about 13 days are male, the slightly shorter second shift being predominantly carried out by the female birds. This division of duties in Adelies appears less clear during years of low food availability or in the season after a major catastrophic event, such as a cohort failure (Gardner pers. comm.).

A3 size

Fluctuations in the numbers of birds attending a colony each year can indicate a number of changes, not all of them associated with food

availability. It is useful in giving a broad picture of the survival trends of the colony in comparison with other colonies under study.

A4 survival and

This is a complex demographic parameter. It relies on being able to identify individual birds nests and following their progress over successive years. It also monitors young birds (recruits) on joining the colony. Winter food supply is a crucial factor.

AS Duration of

This parameter is dependent not only on food availability but the time and distance required to travel to obtain that food. Where telemetric devices have been used to track the birds, it is possible to correlate these tracks with locations of krill fishery, indicating a possible conflict (Kerry, Clarke et al. 1995). It is a useful parameter as trip duration is related to prey location, especially if large amounts of data can be gathered using automated devices.

A6 success

Interannual variations in breeding success at a colony can give much indirect information on environmental conditions over winter, food availability integrated over the year and general health of the birds. A7 Chick at

This parameter again is a combination of a number of factors. It is affected by prey availability, distance of prey from the colony and the parents' breeding experience. It is assumed that lighter chicks have a reduced chance of survival over winter.

AS Chick diet

This is ascertained by catching breeding birds as they return from foraging trips and inducing them to regurgitate their stomach contents using la vage133 before they reach their chicks to feed them. The stomach

contents are subsequently analysed and food species are identified. Where this procedure is carried out in conjunction with satellite tracking of birds, a very rough estimate can be made of prey location. The lavaging procedure can be distressing to birds, although it does not appear to discourage them from returning to the colony134. Occasionally birds die from it. A more benign method, for which procedures have not yet been worked out, would be to obtain samples of faeces for analysis (Lawless, Clarke pers. comm.). Clarke further suggests that weight gain data

give diet composition and an estimate of mass of food consumed with less stress on the birds than complete flushing.

Where birds are feeding predominantly on krill, there is good correlation between weight gain and stomach contents mass. If the diet is mostly fish, much is lost in the sieving procedure and thus there is underestimation of food eaten (Clarke pers. comm.).

A further point to note is that AS requires chick diet at the creche stage only. Clarke is of the opinion that it is probably just as important to monitor chick diet during the guard stage as it may differ from that of the creche phase. Chicks are more liable to starve during the guard phase (Clarke pers. comm.). This method clearly requires further study.

This provides basic information necessary for the sensible application of some of the other methods, namely Al, A3, A6 and A7. Like Method AS, it is invasive to individual birds, requiring marking of their bodies.

Frequent visits to nests to ascertain presence of eggs or chicks can result in egg losses, increased predation by skuas and nest desertions. Nests nearby are likewise disturbed by the visits of personnel. Over the longer term, a gradual shift away from formerly monitored nests to new nest sites elsewhere in colonies has been observed. Young birds are also

discouraged from entering the colony by too obvious human presence. These effects are noted in the Method, but the only advice that it gives to scientists is to 'walk slowly'. Revision of this method is needed to

overcome or minimise these problems.