first calendar year: June

Last update of this page: 31-07-05 21:40

In breeding season 2004 we started a survey amongst 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. 

  • In the 1cy LBBG May Section you can find a draft version of the research proposal.
  • This June section presents some data on egg size & comparison to previous years.

In June most Dutch adult LBBG can be found with pulli. Two chicks is an average, but in year 2004 several parts of the colony were destroyed by construction works and activities. On June 03 and June 25 2004, mowing activities killed several young in the margins of the colony. 

Most selected nests were equipped with wooden fruit boxes to shelter the pulli. We marked and measured eggs and checked nests on presumed hatching date. Pulli were ringed and body mass were weighted. From June 18 2004, small plastic tie wraps were replaced for large darvic rings. We used telescopes and video / camera to score wing coverts and scapulars on second generation feathers. 

In this 1cy LBBG survey we wanted to be able to correlate the presence of second generation feathers to the date of hatching. For this reason, the complete sample has been divided in three categories: early hatching, intermediate and late hatching pulli. Quite arbitrary, the periods for hatching were set to:

  1. Category I - "so-called 100 nests" (early hatching): pullus hatched before June 10; 
  2. Category II - "so-called 200 nests" (intermediate hatching): pullus hatched between June 10 and June 20; 
  3. Category III - "so-called 300 nests" (late hatching): pullus hatched after June 20.

Knowing that the incubation period for LBBG eggs is about 30 days, we started marking nests from late April. While marking the nests, we could measure egg volume fairly easy. Data are presented in tables 1 and 2 below.

Tables 1cy LBBG June:

Table 1: comparison of egg measurements 1992, 1993, 2004 for colonies Maasvlakte & Europoort (Dintelhaven), the Netherlands.
colony, year Length
(in mm)		 SD Width
(in mm)		 SD Volume
(in cm3)		 SD N
Largest egg
Maasvlakte 1992 67.34 2.5 47.89 1.3 74.65 4.7 30
Maasvlakte 1993 67.64 2.5 47.51 1.2 72.70 4.1 49
Maasvlakte 2004 67,50 3,6 46,52 1,5 69,72 6,9 29
Europoort 1992 67.58 2.7 47.58 1.3 72.90 5.3 73
Europoort 1993 67.02 2.9 46.80 1.4 69.98 5.5 42
Europoort 2004 66,79 2,6 46,93 1,5 70,14 5,9 37
Middle-sized egg
Maasvlakte 1992 67.32 2.3 47.16 1.6 71.36 5.4 30
Maasvlakte 1993 66.46 2.3 46.89 1.2 69.62 4.5 49
Maasvlakte 2004 66,16 3,4 46,56 1,4 68,43 6,7 25
Europoort 1992 66.57 2.8 46.99 1.4 70.08 5.8 73
Europoort 1993 65.61 2.9 46.07 1.4 66.43 6.0 42
Europoort 2004 65,77 2,4 47,07 1,6 69,48 5,9 31
Smallest egg
Maasvlakte 1992 65.76 2.4 45.62 1.6 65.26 5.5 30
Maasvlakte 1993 64.72 2.3 45.37 1.3 63.48 4.5 49
Maasvlakte 2004 64,47 3,7 45,36 1,6 63,35 7,3 19
Europoort 1992 64.87 2.9 45.51 1.8 64.06 6.1 73
Europoort 1993 64.28 2.7 45.02 1.6 62.15 5.9 42
Europoort 2004 63,37 2,1 46,14 1,2 64,28 4,4 23
Notes:
Variation between sample sizes 2004: some A-eggs were measured as the sole egg in a nest, but later observations of a full nest (3 eggs) confirmed it was indeed the A-egg. B & C-eggs from same nest not measured.
Data from: A.L. Spaans, et all; The relationship between food supply, reproductive parameters and population dynamics in Dutch Lesser Black-backed Gulls Larus fuscus, a pilot study; IBN Research Report 94/9.

 

Table 2: analyses for 3-egg clusters Maasvlakte and Europoort 2004. In cm3.
totaal sample Maasvlakte  Europoort (Dintelhaven)
Average 67,61 67,44 67,76
Median 66,96 67,34 66,81
Modus 62,77 #N/A 72,04
Standard deviation 6,67 7,76 5,66
Sample variance 44,46 60,23 32,08
Minimum 50,87 50,87 53,81
Maximum 83,66 83,66 80,45
N 126 57 69
Confidence interval (95%) 1,16 2,01 1,34
t-test 2,2 0,79
Notes:
Volume after Harris 1964. V in cm3. V = 0.476*length*with2
Largest Volume: 83,66. Nest 196 at Maasvlakte, A-egg (72,9x49,1); measured April 29 2004 (Category I), clutch 3 eggs.
Smallest Volume: 50,87. Nest 257 at Maasvlakte, C-egg (64,7x45,9); measured May 16 2004 (Category III), clutch 3 eggs.

 
1cy lbbg in June. (87036 bytes)LBBG 1cy, June 03 2004, Maasvlakte, the Netherlands. 
Nest 375.
4399notes.jpg (68775 bytes) LBBG 1cy, June 03 2004, Maasvlakte, the Netherlands. 
Taking notes on data sheets.
4559prims.jpg (97387 bytes)LBBG 1cy, June 10 2004, Maasvlakte, the Netherlands. 
Measuring wing when pulli are older than 5 days.
1cy lbbg in June. (101824 bytes) LBBG 1cy, June 03 2004, Dintelhaven, the Netherlands. 
Nest 101.
1cy lbbg in June. (62628 bytes) LBBG 1cy, June 03 2004, Dintelhaven, the Netherlands. 
Nest 101.
1cy lbbg in June. (72807 bytes) LBBG 1cy, June 03 2004, Dintelhaven, the Netherlands. 
Nest 100.
4603theo.jpg (99876 bytes)LBBG 1cy, June 10 2004, Maasvlakte, the Netherlands. 
Theo Muusse at "EMO field", nests 130 - 138.
4571tail.jpg (79202 bytes)LBBG 1cy, June 10 2004, Maasvlakte, the Netherlands. 
Tail and primaries growing. Nest 137.
8202tn.jpg (75593 bytes)LBBG 1cy, June 18 2004, Oostvoorne, the Netherlands. 
Theo & Norman.
8206makingrings.jpg (59918 bytes)LBBG 1cy, June 18 2004, Oostvoorne, the Netherlands. 
The making of...
8289bj.jpg (82453 bytes)LBBG 1cy, June 18 2004, Dintelhaven, the Netherlands. 
Bert-Jan Luijendijk with several pulli.
8224e786.jpg (96837 bytes)LBBG 1cy E786 & E788, June 18 2004, Dintelhaven, the Netherlands. 
Nest 105.
8284tbj.jpg (82491 bytes)LBBG 1cy, June 18 2004, Dintelhaven, the Netherlands. 
Bert-Jan Luijendijk and Theo Muusse measure pullus E42.
8246norman.jpg (85812 bytes)LBBG 1cy, June 18 2004, Dintelhaven, the Netherlands. 
Norman van Swelm.
8256fullhouse.jpg (96941 bytes)LBBG 1cy, June 18 2004, Dintelhaven, the Netherlands. 
Full House.
8288tbj.jpg (82171 bytes)LBBG 1cy, June 18 2004, Dintelhaven, the Netherlands.
Theo and Bert-Jan.
8315e50.jpg (68016 bytes)LBBG 1cy, June 18 2004, Dintelhaven, the Netherlands. 
Theo with red E50.
8325release.jpg (85065 bytes)LBBG 1cy, June 18 2004, Dintelhaven, the Netherlands. 
Release and relieve...
1cy lbbg in June. (94360 bytes)LBBG 1cy E41, June 25 2004, Dintelhaven, the Netherlands. 
Nest 109.
5063e43.jpg (116245 bytes) LBBG 1cy E43, June 25 2004, Dintelhaven, the Netherlands. 
Nest 108.
5070e49.jpg (91818 bytes) LBBG 1cy E49, June 25 2004, Dintelhaven, the Netherlands. 
Nest 108.
1cy lbbg in June. (79376 bytes) LBBG 1cy E46 & E52, June 25 2004, Dintelhaven, the Netherlands.
Nest 110.
5085n399c.jpg (94945 bytes) LBBG 1cy E74, June 25 2004, Maasvlakte, the Netherlands. 
Nest 109.
1cy lbbg in June. (85009 bytes) LBBG 1cy E789 & E796, June 25 2004, Dintelhaven, the Netherlands.
Nest 103.
5097e59.jpg (112928 bytes)LBBG 1cy E59, June 25 2004, Maasvlakte, the Netherlands. 
Nest 137.