I have read that only some 15% to 25% of nestlings that fledge from a given colony can be expected to survive their first year. I have also read that only some 10% of nestlings that fledge from a given colony can be expected to return to that colony as SY birds.
For the sake of clarity and discussion, lets assume that the survival rate of fledglings which ranges from 15 to 25% is actually 20%. If that is the case then isn't the actual percentage of fledglings that return as SY birds really 50% of those that survive?
Natal Dispersal Question
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John & Linda - KY
- Posts: 599
- Joined: Wed Nov 12, 2003 10:19 pm
- Location: Kentucky/Hawesville
It would be if no returning fledglings went to a different colony, but they do. -- John
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Bob Rogers
- Posts: 226
- Joined: Sun Feb 15, 2004 6:48 pm
- Location: Arnold, Missouri
oneidalaker,
I have read the same numbers that you spoke of for PM mortality rates. While I'm sure it was written whith some study and knowledge, I too ponder over such a poor return rate of all PM's, let alone the SY's. I know nature takes an annual toll, but, if that is the correct number, how do you explain the rapid growth of many colonies within only several years? The projected survival rates may be correct for many unmanaged colonies --- many barely surviving over the years, but I believe well managed sites in good to excellent real estate, the rate of success is far better.
I have read the same numbers that you spoke of for PM mortality rates. While I'm sure it was written whith some study and knowledge, I too ponder over such a poor return rate of all PM's, let alone the SY's. I know nature takes an annual toll, but, if that is the correct number, how do you explain the rapid growth of many colonies within only several years? The projected survival rates may be correct for many unmanaged colonies --- many barely surviving over the years, but I believe well managed sites in good to excellent real estate, the rate of success is far better.
Bob R.
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Guest
You know those numbers are just the averages they come up with when a particular survey is done. If you think about somebody that's sitting on a big block of ice while their hair is on fire on average they are about the right temperature...! Taking this scientific interpulation into consideration I am certain you'll have an average increase in the population of your colony next year.