Lesser Black-backed Gull (graellsii & intermedius)

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first calendar year: May

In breeding season 2004 we started a survey among 1cy Lesser Black-backed Gulls to describe the presence of second generation feathers and commencement of the post-juvenile moult while the birds are still attending the parents for food in the colony. 
In the sections of 1cy LBBG for the months May, June, July and August, we will enlarge upon this survey and publish data later this year.

RESEARCH PROPOSAL LBBG 1CY POST JUVENILE MOULT
(draft version 07 February 2004 - ORG)

ABSTRACT

This research will describe the development from downy plumage into full juvenile plumage in 1cy Lesser Black-backed Gull. Furthermore, it will show that juvenile LBBG, which still frequent the colony and attend the parents for food, do or do not commence the post-juvenile moult as early as August. For this reason, about 60 pulli from almost 200 nests will be ringed in breeding season 2004 in the Maasvlakte colony near Rotterdam, the Netherlands.

The total group will be split into three sub-groups, depending on egg-laying date and hatching date of the chicks: hatching at about 1st June : 25 nests ("group 100"); hatching data at about 15 June : 20 nests ("group 200"); hatching date at about 01 July : 20 nests ("group 300"). Out of the complete cluster of "group 100" nests (the early nests), we select 15 nests to describe in detail the plumage development by visiting these nests 3 times a week. We will check both left wing and right wing and documented details by digital photo's and video.

All nests of project pulli and the direct surrounding of the nests will be checked until at least 10 days after the last observation. This research will also allow statements about feathers which have a second-generation pattern and look relatively fresh compared to adjacent feathers.

INTRODUCTION

Objectives:

• General overview of plumage development in Dutch juvenile LBBG.
• Estimation of age of scapulars and wing-coverts which show a second-generation pattern in juvenile LBBG.

Purpose:

Juvenile LBBG are believed to be slow starters regarding post-juvenile moult, although some literature mention the period directly after fledging as initiation period. Currently it is believed that juveniles which moult early in autumn, only include several upper scapulars in this process. This research will quantify birds, which start moult in the colony, to get a better understanding of initiation date and better understanding of patterns in first and second-generation wing-coverts and scapulars.

• Select birds which show second-generation like feathers and check their histories.
• Analyse moult sequences in scapulars, tertials and wing-coverts, related to hatching date, age in days and primary length.
• Describe possible patterns and types of early-required and late-required feathers in juvenile LBBG.
• Determine whether the post-juvenile moult may take place before 15 August.

Goals:

Describe the moult sequence in scapulars and wing-coverts, related to hatching date en age in days. Publish information on moult sequences and feather patterns in juvenile LBBG.

RATIONALE

On 13 July 2002, 3% of juvenile LBBG in the Maasvlakte colony showed missing feathers in the scapulars (in a sample of 99 birds) and none of these birds showed second-generation like feathers. August 16 2001, an estimated 60% of begging juvenile LBBG (sample of 32) in the Maasvlakte colony already showed second-generation like scapulars and/or wing-coverts. It is known that the post-juvenile scapular moult may start right from fledging, but such early moult in the colony (including wing-coverts) has not been described yet.

In this research, we define the ordinary moult sequence from literature and from the majority of birds, represented by an "early hatching" control group. We will select the initiation loci and sequences in moult waves. When feathers are left out of this basic sequence for any reason, this is scored (individual missing feathers are scored as missing or as moult gaps in growing rows). The sequence may also be classified "different", in birds which show random moult schemes.

If feather patterns are obvious different, one may expect these different patterns on the last required feathers, moulting in in the former moult gaps. This research must reveal whether fresh second-generation like scapulars and wing-coverts are either late required first generation feathers or feathers replaced in the post-juvenile moult, hence already second generation.

QUESTIONS AND HYPOTHESES

H0: Scapular and covert moult sequence is function in time.

Ha: Scapular and covert moult sequence associate with primary moult.

Hb: Scapular and covert moult is a function of hatching date.

H0: Last required scapulars or wing-coverts show a different pattern.

Ha: Last required scapulars or wing-coverts show the ordinary pattern.

Hb: Scapulars or wing-coverts with a different pattern are second-generation feathers, required in the post-juvenile moult.

H0: Juvenile LBBG follow a standard moult sequence in scapulars & wing-coverts.

Ha: Juvenile LBBG normally show a jumping sequence in this moult.

Hb: Juvenile LBBG do not follow any standard moult sequence in scapulars & wing-coverts.

METHODS:

1. Preliminary research: information on the ordinary moult sequences in juvenile large gulls / other bird species (February - May 2004).
2. March: determine emigration dates of adult LBBG from the colony after breeding based on 2003 data.
3. March: selection of 30 breeding pairs that most probably will have egg-laying date in the first decade of May 2004 (group 100). Depending on nest location and observation conditions, this group 100 will be split later into two groups, group 100a and group 100b.
4. March: selection of 20 nests with egg/laying date between 15-30 May (group 200).
5. March: selection of 20 nests of ringed adults with pulli, which were seen late in the season in the colony in breeding season 2003, egg/laying date between 01 - 14 June (group 300).
6. 01 - 30 April: 5 visits to select territories and draw maps on locations. This can be the same map as the map used in the adult LBBG project. When territories are confirmed in a second visit, these territories will be marked in the field by sticks with ring-code. Locations: BP, Eurorama, EMO, Nachtegalenkeet.
7. 01 - 10 May: egg/laying in 30 nests of group 100. Note the dates of A-B-C eggs and mark the eggs with permanent markers. Analogously to Vercruijsse Herring Gull research. Also measurements to determine egg volume.
8. 01 - 15 May: selection of nest locations of group 200: 20 nests.
9. 30 days breeding interval group 100.
10. 15 - 30 May: determine egg/laying date for group 200. Note the dates of A-B-C eggs and mark the eggs with permanent markers. Analogously to Vercruijsse Herring Gull research. Also measurements to determine egg volume.
11. 15-30 May: selection of nest locations of group 300: 20 nests.
12. 1^st week June: 1 week before hatching date, we place walk-in cages to catch adult LBBG and score phenologic characteristics. Scores with colour scales, measurements, weights and digital photographs.
13. 01-02 June: the group 100, containing van 30 pairs will be split: 15 nests will be supplied with wooden boxes to shelter pulli and will be fenced to prevent wandering pulli and make taking measurements easier (group 100a).
14. 1^st week of June: determine egg/laying date for group 300. Note the dates of A-B-C eggs and mark the eggs with permanent markers. Analogously to Vercruijsse Herring Gull research. Also measurements to determine egg volume.
15. 01-15 June: determine hatching date of pulli from group 100.
16. 05 June - 15 July: pulli of group 100a will be tie-wrapped when the oldest pullus is at least 5 days of age. Stress on the moult sequence of juvenile feathers (photos) + 3*/week measurements of key factors:

• Total leg -/- nail.
• Head + Bill.
• Weight.
• After day 5 also hand span.
• Sequence of wing-covert growth

17. 01 June - 15 July: 3x/week video/photos of group 100b (about 15 July = fledging). Stress on second-generation like feathers on left wing and right wing.
18. 2^nd week June: 1 week before hatching date, we place walk-in cages to catch adult LBBG of the group 200 and score phenologic characteristics. Scores with colour scales, measurements, weights and digital photographs.
19. 15-30 June: hatching group 200.
20. 20-30 June: ring (tie/wraps) and measure of pulli from group 200.
21. 20 June - 31 July: photograph or video the left wing and right wing of group 200. Stress on second-generation like feathers.
22. 4^th week June: 1 week before hatching date of group 300, we place walk-in cages to catch adult LBBG and score phenologic characteristics. Scores with colour scales, measurements, weights and digital photographs.
23. 01 July - 07 July: hatching of group 300.
24. 01 July - 07 July: darvic rings on pulli of group 100a and 100b.
25. 05- 10 July: ring (tie/wraps) and measure pulli from group 300.
26. 10 July - 15 August:  photograph or video the left wing and right wing of group 300. Stress on second-generation like feathers.
27. 15 July - 20 July: darvic rings on pulli of group 200.
28. 30 July - 05 August: darvic rings on pulli of group 300.
29. At least 10 gays after last sightings of pulli, visits continue at the breeding locations of project birds in the colony.
30. Additive: when Norman will ring pulli with darvic rings, we include the measurements and weights as reference and control group. Also photograph birds and look for second/generation like feathers.
31. Compute data (August - November 2004).
32. 1^st version of publication (November 2004).
33. Compute comments (December 2004).
34. 2^nd version of publication (February 2005).
35. Compute comments (March 2005).
36. Publication (April 2005).

Project organisation:

1. Project coordinators: Theo & Mars Muusse.
2. Preliminary research: Mars & Theo (incl: key factors for relation hatching date in downy pulli, common moult sequence in juvenile birds from literature).
3. Ringer: Norman van Swelm.
4. Observers: Theo, Mars; additional BJ, Ruud.
5. Data processing: Mars & Theo.
6. Data analysis: ORG
7. Writing article: Mars & Theo.
8. Finance: pm.

1. Develop standard sheets for notes on moult loci & 2nd generation like feathers: Mars.
2. Video-camera and video-tapes: Mars.
3. Darvic rings: Norman, and tie-wraps: Theo.

All pulli born from adult-project birds will be ringed.

We use chicken-fence walk-in cages (50x80 cm) to catch adult birds, 2 - 3 weeks after egg-laying. When caught, notes will be taken (including exact time) and adults will be darvic ringed. Measurements on adults:

• Total leg -/- nail. Vernier callipers readings to 0.1 mm: from feathering to stretched mid-toe -/- nail.
• Head + bill. Vernier callipers readings to 0.1 mm: bill-tip to back-head bump.
• Gonys-height to 0.1 mm.
• Bill-depth to 0.1 mm.
• Hand span. Ruler readings to 1 mm.
• PMS (= primary moult score). Photographs of unfolded wing: portray primaries and secondaries.
• Leg colour measurements using yellow scale (+ photo showing both leg and scale).
• Bill-colour using yellow scale (+ photo showing both bill and scale).
• Size of gonydeal spot (photo showing spot reaching upper mandible yes/no).
• Pigmentation of iris from photos.
• Colour of orbital ring using red scale (+ photo showing both eye and scale).
• Pattern primary tips P9-P10 photo + measurements to 1 mm.

15 nests will be fenced (about 50 m²) and we place wooden fruit boxes to shelter pulli (group 100a).

Group 100a pulli will be measured every 3 days, until they leave the fence. From then on, they will only be videoed and photographed.

Measurements pulli group 100a:

• Total leg -/- nail. Vernier callipers readings to 0.1 mm: from feathering to stretched mid-toe -/- nail.
• Head + bill. Vernier callipers readings to 0.1 mm: bill-tip to back-head bump.
• Weight. Place bird in bag attached to unster. Readings to 1 gram.
• Hand span. Ruler readings to 1 mm, measurements from chick age = day 05.
• Sequence of wing-covert growth. Unfold wing and photograph scapulars, wing-coverts and tertials. Use designed forms to note location of unusual patterned wing-coverts or scapulars.

By 15 June all pulli are still present and can be caught to attach tie-wraps. By 10 July the first groups leave the colony, P9-P10 still growing. During this period, 15 visits will be planned.

Every tie-wrapped pullus will be checked on both left wing and right wing by video-taping or photographs. Field observations for primary moult stage. Just before fledging, pulli are caught again and will be ringed with darvic rings. They will also be measured and weighted.

When video-taping, comment on: date, observer, ring number, visible moult scores in the following order: tertials, gr covs, med covs, low les covs, les covs, Recs, Prims, scaps and location of 2^nd gen like feathers.

Describe moult sequence of coverts and scapulars (basic order).

Equipment checklists:

1. Video camera, tapes, battery.
2. Digital camera.
3. Map with nest locations.
4. Wooden sticks to mark nests.
5. Plastic / chicken rings or tie-wraps.
6. Gull illustration forms to locate moult loci.
7. Vernier callipers to 0.1 mm; Ruler to 1mm; Unster to 1 gram.
8. Chicken fence made walk-in cages 50 x 80 cm.
9. Tie-wraps, paperclips.

STATISTICAL METHODS:

Sampling:

• The LBBG-juvenile project at Maasvlakte Rotterdam will be linked to the LBBG adult-project 2004, which will focus on moult. In this project, one of the parents must have been ringed as pullus and the nests are chosen randomly, a-select. These a-select nests will result in a-select pulli. There is no bias or no logic in constructing relationships between parents carrying darvic rings and the presence of second generation-like wing-coverts and scapulars in pulli.
• Sample size: success rate at Maasvlakte is between 0-3 pulli, average is one. With 70 nests selected, we estimate about 70 project-pulli.
• 13 July 2002 we scored juveniles. 3% showed a few missing scapulars. In 2001, we scored birds later in the season, resulting in 60% of the juveniles showing second generation-like feathers in birds still attending the parents by mid August. The presence of these second generation-like feathers seems to be related to date. Therefore we will split the complete group of 70 nests:
• 25 nests. Egg-laying 01-15 May, bulk in the colony (group 100a & 100b).
• 20 nests. Egg-laying 15-30 May, slightly late pulli (group 200).
• 20 nests. Egg-laying 30 May - 15 June, late pulli. (we know late nests are less productive (e.g. more predation). We hope to follow 8 pulli from this cluster = 45% success rate compared to group 100.
• We score moult sequences on special forms.
• We will compute in Excel sheets.

Descriptive statistics:

• Linear regression for mass increment - age in days.
• Linear regression for hand span in mm - age in days.
• Linear regression for growth (leg/head) - age in days.

Hypotheses (null and alternative):

Wing-covert moult stage is a relation of hatching date en dependant on primary moult score (TOT COV = α + βt_h + γPMS):

• H0: these three variables associate.
• Ha: these three variables do not associate.

 Wing-covert sequence:

• H0: juvenile LBBG follow the ordinary moult sequence in wing-coverts.
• Ha: juvenile LBBG do not follow the ordinary moult sequence in wing-coverts.

Commencement of post-juvenile moult in the colony:

• H0: N_{scap 2g} + N_{cov 2g} = 0 (t< 15 August)
• Ha: N_{scap 2g} + N_{cov 2g} > 0 (t< 15 August)

Analytical procedures / Data analyses:

We use excel sheets: lbbgpostjuv2004. This sheet will contain:

• Individual code, ringcode, side;
• Date: 01 January = 1 in adult research;
• WC: wing-covert sequence (code 0-4) derived from standard forms to answer RESEARCH QUESTION 3;
• PATTERN: feather patterns (code A-B), to answer RESEARCH QUESTION 2;
• PMS: 10 - 50, per primary 1-5 (code 0 absent) in adult research;
• Fully grown juv TT, GC, MC, LLC, LC in classes 0-5 (=0,0-25,25-50,50-75,75-100,100);
• Total juv covert moult score en % score, to answer RESEARCH QUESTION 1;
• US, LS, TOT SCAPS  for scapulars score in first generation juvenile feathers;
• US, LS, TOT SCAPS  for scapulars score in second generation juvenile feathers, to answer RESEARCH QUESTION 2;
• # 2g TT, GC, MC, LLC, LC;
• Total second generation coverts, to answer RESEARCH QUESTION 2.

PARTICIPANTS

Theo Muusse, Mars Muusse , Bert-Jan Luijendijk, Ruud Altenburg
Norman van Swelm

REFERENCES

p.m.

ADDITIONAL READING

p.m.