Trees removed, Kapiti Coast

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  • #13210

    Jacqui
    Moderator

    Hi all

    I had a few phone calls this past week about a newspaper article about some pine trees being felled in Paraparaumu – there were a large number of Monarch butterflies in them. It wasn’t clear if this was an overwintering site or a collection point for butterflies migrating to warmer climes (north?).

    The pines were evidently in a dangerous condition and branches were falling off during bad weather.

    A biologist with the Wildlife Service in California gave me his thoughts on what might happen to the Monarchs which were in the trees at the time.

    If the wintering behaviour in NZ is analogous to the monarch butterflies in California, then the effect of the tree cutting will depend upon a couple of factors.

    First, was the site a temporary bivouac or a permanent wintering colony? Bivouacs are sites that form because they have suitable conditions, especially nectar sources, and the animals do not stay for long periods of time; they exist because of the constant stream of butterflies passing through them. Bivouacs form and are most common in the fall, but may also persist through the winter if the weather is mild.

    When environmental conditions reach a certain level, probably low air temperatures, then the insects "settle down" into permanent wintering colonies. These are sites where the monarchs stay and do not move away from them until late January or February when they leave for their migration inland. One can speculate that in a mild winter or in places like southern San Diego County, bivouacs can persist through the winter (but even San Diego County can have winters with freezing or very cold temperatures).

    The best way to tell if the Monarchs are moving through a site (temporary bivouac) or staying (permanent wintering colony) is by marking them.

    Secondly, are there any alternative sites nearby for them to utilise? If not, then the animals have a problem, especially if the weather conditions are such that they will die if they are unable to fly great distances (e.g. too cold, rainy, etc). The colonies, especially permanent wintering colonies form because of specific environmental conditions, especially wind protection.

    Third, in California, the Monarchs seem to use a number of sites in an area for bivouacs and permanent wintering sites. The loss of one site or a few may not affect them very much, but if too many sites, or critical ones that maintain the environmental conditions needed for them to survival during harsh winters, then conceptually this could lead to the collapse of the wintering butterflies in a specific area.

    Fourth, and this may not be an issue in NZ, the tremendous amount of development in the Central Valley and Sierra Nevada foothills may have eliminated areas containing milkweed where the butterflies build their numbers in the spring, summer and early fall, and caused a decrease in the number of Monarchs. The last two items are speculative indeed at this point.

    Temporary bivouac sites may ‘turn into’ permanent wintering colonies; that is the butterflies stop moving around and remain at a site through the winter. But some bivouac sites do not possess the environmental conditions necessary for their winter survival, and they disappear as the stream of Monarchs passing through ends.

    Dr. Leong has done good work on what the conditions are at the colonies. I do not think the animals ‘know’ a site contains the factors that will allow them to survive the winter, but as air temperatures drop and day length decreases (and other factors?), they remain at the sites that have the proper conditions for their survival. This could be why some sites in California have wintering Monarchs some years and not in others.

    Temporary bivouacs often have a nectar source, but I am not sure if that is the primary reason why they form at sites – it may be the animals are simply ‘searching’ for suitable sites to survive the winter, and as conditions change as winter approaches, they lose the environmental elements being sought by the butterflies.

    I can find no records of anyone ever having reported these trees as an overwintering site – I am hoping that the local newspaper will print the information I have sent them so more people in the area will get involved in looking for tagged Monarchs. We already have several people tagging in the area.

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  • #18400

    haluca1
    Participant

    Hi Jacqui, will certainly try – my copy has already gone out with the recycling but am trying to find another copy, will let you know how I get on.

    #18389

    Jacqui
    Moderator

    Hi Haluca

    No I didn’t know the letter had been published – would be grateful if you could cut it out and send it to me. 27 Matauwhi Road, Russell.

    Thanks heaps.

    J.

    #18388

    haluca1
    Participant

    Jacqui, I’m sure you’re already aware but your letter was printed in the paper this Thursday – I wasnt surprised to see it! I saw the original article and although I didnt find the time to come on here and say it was there, I was glad to see you had heard of it. I live about five minutes drive from where the trees were, but havent been to that park since I was at school around ten years ago (local rugby and netball is played there). I hope they’ve found a new home, esp if any of my tagged ‘babies’ are amoung them!

    #18364

    Jacqui
    Moderator

    More on the subject:

    ——– Original Message ——–
    Date: Sun, 6 Jul 2008 22:04:41 -0400
    From: Mona Miller <mona.miller@cox.net>

    http://www.uuottawa.com/urquhart_fred.htm
    ” The home range of the monarch has exploded from North America and Central
    America to most of the world between 45 degrees north and south
    (Urquhart,1987). The North American population exhibits a yearly migration
    for which it is well known, but is the only population known to do so. The
    Columbus Hypothesis offers one explanation for these phenomena. According
    to this theory, the North American population has not always migrated, but
    began doing so after the arrival of European colonists. The Europeans
    destroyed much of the forest that covered North America, and was replaced by
    milkweed, an opportunistic species that flourished in the deforested areas.
    The spread of this weed enabled the monarch population to spread as well,
    resulting in an overspill which eventually colonized a large part of the
    temperate regions of the world. Furthermore, there is no evidence that
    monarchs performed such long migrations before about 1865. The fact that
    populations found in all other regions do not migrate so extensively (in
    Australia, for example) suggests that this migratory behavior evolved in the
    North American population after other populations had become established
    elsewhere (Vane-Wright,1193). However, this theory may need some refinement
    in the face of findings that monarchs guide themselves on their migrations
    by use of an internal magnetoclinic compass (Schmidt-Koenig,1993). It seems
    doubtful that such a trait could have evolved in so short a time, but
    another explanation could be that other populations have simply lost this
    guidance mechanism.”

    Mona Miller
    Herndon, VA (USA) }i{ }i{ }i{

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