I've been off-campus all week chaperoning students, but finally got to do a nest-check today.
With twenty-nine broods observed it is official: an average brood size of only 3.1 young/nest. There were some obvious runts in a couple of four- and five-nestling broods so I expect the average brood count to fall even lower than it is.
In terms of young produced per nest, this will likely be our least-productive martin year ever in our nine years of martineering. I can only assume that the effects of our lingering drought are the probable cause.
Adding insult to injury, a whole clutch of eggs (or more likely newly-hatched young) has disappeared from a Big Bo.
On the bright side, a vanished clutch of five eggs in a Supergourd have been replaced with five new martin eggs. Also, only one of our forty gourds (a Carrol), is now showing no signs of martin activity.
Interestingly, our presumed oldest martin pair, our first arrivals on-site back in January, presently have SIX vigorous and healthy-looking young with no apparent runts. If indeed the pair presently occupying that east-facing Natureline are those same two early martins, we may be witnessing the power of experience.
Our colony as of today:
8 crescent Big Bos: 7 gourds with young, 1 empty nest.
8 round-hole Carrols: 6 gourds with young, 1 nest with eggs, 1 nest start showing no activity.
8 crescent Naturelines: 5 gourds with young, 2 gourds with eggs, 1 nest under construction.
8 crescent Naturelines w/cling rod: 6 gourds with young, 2 gourds with eggs.
8 WDC Supergourds: 5 gourds with young, 3 nests with eggs.
Mike Scully
School Colony Update: 3.1 young/nest
Hi Scully,
At the risk of sounding stupid, why would eggs disappear from your Big Bo? I assume you have predator guards. One of the reasons I am asking is that the same thing happened to a clutch of Chickadee eggs along the BB trail I monitor. There is a predator baffle. From what I understand, only a snake will go in, eat the eggs and leave the nest "untouched"? It amazes me that a snake can climb a stainless steel , built-to-proper-specs baffle.
At the risk of sounding stupid, why would eggs disappear from your Big Bo? I assume you have predator guards. One of the reasons I am asking is that the same thing happened to a clutch of Chickadee eggs along the BB trail I monitor. There is a predator baffle. From what I understand, only a snake will go in, eat the eggs and leave the nest "untouched"? It amazes me that a snake can climb a stainless steel , built-to-proper-specs baffle.
Fledge on!
Nanette
Nanette
Rather than predator guards, we have "vandalism guards" (see http://www.nisd.net/jay/martins/VandalsS&S.htm ), snakes and raccoons not having been a problem at our urban site. I don't know that either sort of predator could climb our vaseline-coated pole guards. If they did they left no marks of their passing on the poles.
While the earlier Supergourd eggs that disappeared apparently really were removed while eggs (the last two being found in the WDC entrance tunnel), it seems equally likely that the six eggs in the Big Bo hatched, the small nestlings then being thrown out.
In the absence of broken/pecked eggs in and around the gourds, I'm guessing SY martin males to be a likely culprit. Both gourds have SREH's barring starlings, and no sparrows were observed hanging around the gourds (although it is possible that one came and went).
Upon checking records today, it has become apparent that a clutch of 3 eggs in a Carrol gourd is seriously overdue to hatch (if indeed these are the same three eggs first noted on 4/17). Two lost clutches plus one failure to hatch is not unsual, given that we have had a total of at least 38 clutches now. Our colony was smaller in previous years, and losing a couple of clutches has been an annual phenomenon.
More alarming this year has been an unsually high failure rate of eggs to hatch in nests where some of the young have hatched. Our egg counts are never exact (we do not fish around aggressively in the nests), but our failure to hatch rate in these gourds appears to be around one-third or more. In two clutches of five eggs, only one nestling apiece hatched.
This high egg failure rate is perhaps a blessing in disguise given that three young appears to be about optimal for most of our martins pairs in this dry year.
On our martin cams, one of a brood of four in a Big Bo, an obvious runt, quietly disappeared last week. On our other martin cam in a Supergourd four young hatched last week, but one already is falling seriously behind.
Mike Scully
While the earlier Supergourd eggs that disappeared apparently really were removed while eggs (the last two being found in the WDC entrance tunnel), it seems equally likely that the six eggs in the Big Bo hatched, the small nestlings then being thrown out.
In the absence of broken/pecked eggs in and around the gourds, I'm guessing SY martin males to be a likely culprit. Both gourds have SREH's barring starlings, and no sparrows were observed hanging around the gourds (although it is possible that one came and went).
Upon checking records today, it has become apparent that a clutch of 3 eggs in a Carrol gourd is seriously overdue to hatch (if indeed these are the same three eggs first noted on 4/17). Two lost clutches plus one failure to hatch is not unsual, given that we have had a total of at least 38 clutches now. Our colony was smaller in previous years, and losing a couple of clutches has been an annual phenomenon.
More alarming this year has been an unsually high failure rate of eggs to hatch in nests where some of the young have hatched. Our egg counts are never exact (we do not fish around aggressively in the nests), but our failure to hatch rate in these gourds appears to be around one-third or more. In two clutches of five eggs, only one nestling apiece hatched.
This high egg failure rate is perhaps a blessing in disguise given that three young appears to be about optimal for most of our martins pairs in this dry year.
On our martin cams, one of a brood of four in a Big Bo, an obvious runt, quietly disappeared last week. On our other martin cam in a Supergourd four young hatched last week, but one already is falling seriously behind.
Mike Scully
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Guss P O'Brien
I have some accounting questions for martinwatch.
If there is obvious egg dumping, do you count that as "eggs eligible to hatch" and a nesting attempt? Or do you just disregard them altogether? Would you count it as a nest and drive the eggs laid per nest down?
On renesting (eggs or chicks fail and then a new set it laid), do you count that as one nesting attempt or two? I'm sure it is consider just one pair of adult birds and not two. Do you count it as two nests because you wouldn't want run up the eggs laid per nest stat.
For example, 5 eggs laid and fail and discarded. Then, 5 more eggs laid back in the same nest. Would it be 5 eggs laid per nest?
Another example, 4 eggs laid in one nest with 2 eggs laid in an empty compartment. Would it be 3 eggs laid per nest or 4 eggs laid per nest?
If there is obvious egg dumping, do you count that as "eggs eligible to hatch" and a nesting attempt? Or do you just disregard them altogether? Would you count it as a nest and drive the eggs laid per nest down?
On renesting (eggs or chicks fail and then a new set it laid), do you count that as one nesting attempt or two? I'm sure it is consider just one pair of adult birds and not two. Do you count it as two nests because you wouldn't want run up the eggs laid per nest stat.
For example, 5 eggs laid and fail and discarded. Then, 5 more eggs laid back in the same nest. Would it be 5 eggs laid per nest?
Another example, 4 eggs laid in one nest with 2 eggs laid in an empty compartment. Would it be 3 eggs laid per nest or 4 eggs laid per nest?
Good questions. I would like to hear the views of the PMCA and other landlords on this matter.
For our own in-house stats, we figure nest success per pair from the point of hatching. Egg dumping probably occurs but is likely hard to separate at times from a regular clutch. I cannot recall seeing a gourd with more than seven eggs, except where a new clutch has been laid in a gourd where old, failed eggs are still present.
In as much as some pairs losing clutches in our colony may not attempt a renest, our nestling per pair stats may be overstated. On the other hand, we have had martins start clutches as late as early June, SY and ASY birds both. I figure at least some of these late clutches are second attempts after the loss of an earlier set of eggs or young.
Mike Scully
For our own in-house stats, we figure nest success per pair from the point of hatching. Egg dumping probably occurs but is likely hard to separate at times from a regular clutch. I cannot recall seeing a gourd with more than seven eggs, except where a new clutch has been laid in a gourd where old, failed eggs are still present.
In as much as some pairs losing clutches in our colony may not attempt a renest, our nestling per pair stats may be overstated. On the other hand, we have had martins start clutches as late as early June, SY and ASY birds both. I figure at least some of these late clutches are second attempts after the loss of an earlier set of eggs or young.
Mike Scully
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Guest
Strictly from an observers standpoint and if I were trying to get results from recorded stats. I would like to see those stats include all knowns and givens. The multitude of variables as they happen should also be recorded and can/could be classified in there own right.More input to the study can only mean a more informed ending.
dick
dick