Lesser Black-backed Gull (graellsii & intermedius)(last update:
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lbbg 1cy May lbbg 2cy January lbbg 3cy January lbbg sub-ad January lbbg adult January |
adult: Augustadults in the colony In the Maasvlakte colony many adults try to raise two juveniles. As soon as the fledglings can move, the family tries to find a more comfortable place outside the colony, often at the beach or the near fresh water lakes. By the end of August, 99% of the adult LBBG from the Maasvlakte and their juveniles (approximately 70.000 birds) have left the Maasvlakte and start migrating south (at least leave the immediate feeding grounds around the colony). For a while, they gather at the beach, in mixed groups of different age-classes. Several 1.000s of LBBG can be present up to mid September. In these groups the races graellsii and intermedius are both present, but hard evidence to categorize adults to certain races is very difficult, and classification is often only possible when birds are banded / ringed. From mid-October numbers of LBBG decrease rapidly.
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starting date:
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09 Jul
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13 Aug
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20-Aug
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27-Aug
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10 Sep
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week no:
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28
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33
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34
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35
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37
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NEW 0
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115
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3
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2
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1
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0
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NEW P1
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6
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2
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4
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0
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0
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NEW P2
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0
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6
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7
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2
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0
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NEW P3
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0
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7
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10
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12
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0
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NEW P4
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0
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8
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1
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25
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6
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NEW P5
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0
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1
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1
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5
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13
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NEW P6
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0
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0
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1
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0
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11
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NEW P7
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0
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0
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0
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0
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3
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NEW P8
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0
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0
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0
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0
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0
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NEW P9
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0
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0
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0
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0
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0
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NEW P10
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n =
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121
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27
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26
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45
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33
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average NEW P =
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0.0
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2.7
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2.4
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3.7
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5.3
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95% CID =
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0.04
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0.55
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0.55
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0.27
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0.32
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inverse =
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1.98
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2.06
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2.06
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2.02
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2.04
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Variantie (s2) =
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0.05
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1.92
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1.85
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0.82
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0.79
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SD (s) =
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0.22
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1.39
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1.36
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0.90
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0.89
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SE (sx) =
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0.02
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0.27
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0.27
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0.13
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0.15
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% class
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0
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95
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11
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8
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2
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0
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1
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5
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7
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15
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0
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0
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2
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0
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22
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27
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4
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0
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3
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0
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26
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38
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27
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0
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4
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0
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30
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4
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56
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18
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5
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0
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4
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4
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11
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39
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6
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0
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0
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4
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0
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33
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7
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0
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0
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0
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0
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9
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8
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0
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0
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0
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0
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0
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9
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0
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0
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0
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0
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0
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10
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0
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0
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0
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0
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0
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|
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% control:
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100
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100
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100
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100
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100
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NEW0 = no new primaries visible (arrested moult excluded in this analysis). So either P1 still old, or P1 dropped, but the very tip still not visible.
NEW1 = P1 longest new primary. Range between "at least the tip of P1 is visible" until "tip of P2 still shorter than P1".
NEW2 = P2 longest new primary. NEW3 = etc.
Above: Scatter Plot for PMS in adult Lesser Black-backed Gulls throughout the year. Longest new primary is classified "fully grown". Sample size is 2.969 birds. Birds scored on NEW primaries (arrested moult excluded).
Above: Scatter Plot for PMS in adult Lesser Black-backed Gulls. Scoring on longest new primary, which is classified "fully grown" for August (arrested moult excluded). Sample size for this graph is 98 ringed birds.
The earliest date for birds with missing primaries is 30 April 2006, which is not the earliest day in our complete sample. We scored 98 Lesser Black-backed Gulls prior to that date, some already in February. As can be expected, none of these was in primary moult, and this group was excluded in our further analysis as it will only result in a misfit for the onset of moult, using linear regression statistics.
The last scoring days were in November, with a larger sample (133 adults) on 04 November 2010. From that date we have the last birds with retaining old primaries (13 birds with 1, 2 or even 3 old primaries; 120 birds with no old primaries left). From other days in November, only 10 birds were scored (all ringed adults). They all had no old primaries left.
The first tine a new primary (P1) was visible, was on 08 May 2006. Prior to this date, birds were scored missing inner primaries, but the very tip was still not visible (and therefore not scored). As soon as the tip of P1 was visible, this was automatically scored "fully grown" For the other primaries to be scored fully grown, they had to exceed the previous primary in length (so P2 fully grown, only from when it is longer than P1).
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Netherlands
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PMS range
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N:
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Average PMS
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PMS range
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N:
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Average PMS
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1-15 apr
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10
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49
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10
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8-10
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216
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9,9
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16-30 apr
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10
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47
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10
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10
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197
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10,0
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1-15 may
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8-10
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849
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9,8
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8-10
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167
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9,9
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16-31 may
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7-10
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380
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9,7
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7-10
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76
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9,5
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1-15 jun
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8-10
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104
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9,6
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7-10
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33
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8,6
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16-30 jun
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7-10
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253
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9,7
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6-10
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65
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8,2
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1-15 jul
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6-10
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605
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9,2
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5-10
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176
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7,4
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16-31 jul
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-
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-
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-
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4-8
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44
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6,4
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1-15 aug
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3-10
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143
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6,6
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3-10
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165
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5,2
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16-31 aug
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2-10
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1284
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5,4
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3-8
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127
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4,6
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1-15 sep
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1-10
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300
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3,6
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0-7
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234
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3,3
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16-30 sep
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0-7
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645
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2,9
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0-7
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173
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2,1
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1-15 oct
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0-9
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733
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2,2
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0-4
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328
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0,9
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16-31 oct
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0-10
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750
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1,3
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0-3
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244
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0,3
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1-15 nov
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0-3
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138
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0,2
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0-3
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604
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0,1
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16-30 nov
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0
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5
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0
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0-1
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341
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0,0
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LINEAR REGRESSION
Onset of primary moult can best be illustrated by a sinusoid for the first few weeks and last weeks, but there appears to be linear dependency over much of the central moult period.
LINEAR REGRESSION FOR OLD REMAINING PRIMARIES
Complete sample: Linear regression (n = 6171, R2= 0.820, sign: P<0,000)
PMS = -0,381* WEEK + 17,967
Ringed adults: Linear regression (n = 2069, R2= 0.800, sign: P<0,000)
PMS = -0,325* WEEK + 16,270
Unringed adult: Linear regression (n = 4102, R2= 0.779, sign: P<0,000)
PMS = -0,513* WEEK + 23,031
LINEAR REGRESSION FOR NEW FULLY GROWN PRIMARIES
Complete sample: Linear regression (n = 2969, R2= 0.930, sign: P<0,000)
PMS = 0,302* WEEK - 5,933
Ringed adults: Linear regression (n = 1209, R2= 0.888, sign: P<0,000)
PMS = 0,252* WEEK - 4,747
Unringed adult: Linear regression (n = 1760, R2= 0.833, sign: P<0,000)
PMS = 0,442* WEEK - 11,906
Remaining old primaries in adult LBBGs, August 2001. | ||||||||||||||
10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | n: | m: | V: | SD: | SE: | |
15/08: | 6 | 7 | 19 | 21 | 22 | 39 | 18 | 1 | - | 133 | 6,20 | 2,81 | 1,68 | 0,15 |
21/08: | 13 | 10 | 22 | 32 | 43 | 102 | 49 | 2 | - | 273 | 5,82 | 2,67 | 1,63 | 0,10 |
28/08: | 14 | 14 | 25 | 28 | 93 | 158 | 139 | 47 | 1 | 519 | 5,22 | 2,54 | 1,59 | 0,07 |
First cell (10, 15/08 = 6) should be read: on August 15 2001, 6 adults had all 10 primaries old, hence showed no primary moult yet (this is about 4% on 133 observed adults that day). n: observations. m: average. V (= s2): variance. SD (= s): standard deviation. SE (s / sqr n): standard error. |
Survey August 16 2001 Maasvlakte, the Netherlands. Adult primary score in the colony; adults with begging youngs. | |||||||
p3 old | p4 old | p5 old | p6 old | p7 old | p8 old | n: | average: |
1 | 3 | 3 | 2 | 1 | 1 | 11 | 5,82 |
Survey of old primaries in adult LBBG on August 22 2002 at Maasvlakte, the Netherlands (51.57N,04.03E). | |||
Dintelhaven | Missouriweg | Papegaaienbek | |
p1 old | 2 | - | 1 |
p2 old | 4 | 1 | 5 |
p3 old | 8 | - | 8 |
p4 old | 32 | 1 | 10 |
p5 old | 44 | 7 | 14 |
p6 old | 96 | 26 | 12 |
p7 old | 65 | 12 | 9 |
p8 old | 3 | - | - |
p9 old | 1 | - | - |
p10 old | - | - | - |
old prims n old prim m old prims SD old prims SE |
255 5.7 1.28 0.08 |
47 6.0 0.92 0.13 |
59 4.7 1.59 0.21 |
Notes: |
Table below, data for the Netherlands (2000-2010), results for August (aggregated week): number of remaining old primaries in adults.
REM10 = 10 primaries still old (hence, complete moult not started yet).
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