Midcontinent Ecological Science Center, Fort Collins, CO
March 1998
Present: Todd Grant, Leigh Fredrickson, Dave Hamilton, and Rick Sojda

Different approach: evolutionary adaptations

Size of bird

Morphology of bird

• neck length; bill

• age at first breeding

Degree of monogamy

Philopatry

Territoriality

• What is the function of the territory?
• risks

Migration length

Adaptations to herbivory

• gut efficiency

Size

• Big, and predation not really an issue
• Can get to submerged aquatics others can=t get to-especially below ground
• Parts of submerged aquatics (lipids, protein [11-14% fall, 14-16% spring])
• In winter, below ground may be about all that is available to swans
• Swans should be selecting wetlands <3' deep (Holton)
• Opportunistic - selecting high protein/easily digested foods when available
• foliage when available, tubers if foliage not available
• May not arrive on breeding grounds with all needed reserves
• Lower incubation constancy & more feeding during incubation in Tri-State vs. Grand Prairie or Alaska may indicate inability to put on needed reserves which might indicate lower habitat quality
• Leave wintering grounds light
• Use of wintering areas by Tri-State plus Grand Prairie birds
• Is it enough for Tri-State birds, is it too little for all birds?

• Allows swans to get below ground material
• Swans can get food from deep water where it is more easily extracted (geese limited to shallower water with dense root mass)

Grazing on emergents not an important component in Tri-State - may be related to availability (these used by adults & cygnets other places). But, are submergents available to cygnets??

Outside of Tri-State, wetlands with pond lily considered less productive for swans, but most wetlands in Tri-State have pond lily (indicative of stable water)

Longevity

• if live 20 years, how often does a pair need to bring off a brood to maintain/increase the population?
• at Red Rocks, age at first breeding is about 6 years. What about other places?

40+ m band of emergents a key for swan use (Holton)

Does more open area, less convoluted shoreline imply fewer breeding pairs ( i.e., territoriality vs. isolating mechanisms)?

Red Rocks may be about only place where you have more than 1 pair/wetland, partly due to large size of wetlands

• 13 ha/territory @ Red Rocks
• 127 ha/territory @ Grand Prairie

Large-bodied waterfowl model [based on above brainstorming]:

• swans are using endogenous reserves and wintering habitat simply to survive the winter

• the time period during migration and staging/pre-nesting is when the birds bulk-up

• in the Tri-State area, this may be a bottleneck, resulting in females in poor breeding condition - as evidenced by decreased clutch size and decreased hatching success

PRE-NESTING (from time of 1^st arrival on territory, includes nest building & laying)

• arrive light so must put on reserves
• primarily below ground component of submergent vegetation
• <100 cm water (semi-permanent/wetland)
• must be ice-free to forage (but may defend potential nest territory while still frozen)
• within flying distance of nest territory - what is the distance?
• this period is 10-21 days in Alaska
• emergent vegetation with 8-10" water needed for nest construction in Alaska
• Why is there more reliance on muskrat houses & artificial structures in the Tri-State?
• large body size doesn=t require separate thermal cover habitat
• less use in wetlands with <40m edge of emergent vegetation.
• more productive wetlands in WY had diversity of vegetation/inverts, good interspersion, fluctuating water levels (Lockman?)
• occupied territories - older successional stages, no pond lily, more eutrophic, <1m, Chara /Potamogeton
• size of territories varies widely
• would river bulrush & Carex be better than cattail?
• diversity of vegetation would also mean proximity to good emergent vegetation for eventual cygnet foraging
• disturbance at this time can cause territory to be abandoned - disturbance may be more critical during this time than other times of year, and this may limit pioneering new areas or may limit recolonization of an abandoned site

• things change primarily for female and female fasts
• nest building continues throughout incubation
• switch to foraging on emergent vegetation as soon as it became available in Alaska, and probably more foraging on submergents in ID and WY (because emergents not yet available here?)
• proximity of emergents to nest site would allow female to maintain better body condition through incubation
• incubation recesses longer for females in Tri-State than in Alaska - probably due to poorer habitats - takes longer to forage
• 33-37 days

• Potamogeton, Eleocharis, Carex taken by cygnets
• probably have good invert communities
• shallow water heats up early
• adults feeding on same things as cygnets
• escape cover from disturbance - often same as foraging habitat
• What are consequences of the relative lack of emergent habitat in Tri-State?
• adult feeding assistance can help make available vegetation that would not otherwise be
• need dry sites safe from predators - can use nesting sites
• brooding significant in first few weeks
• time to fledge (see Banko) versus growing season length
• adults will be able to find resources for themselves during this period but cygnets may be limited due to restricted habitats they can utilize

Days            Activity
14-21            pre nesting & laying
35                incubation
100-120       to flight stage (80 days in higher quality habitat-
                    may also be day length and diurnal temp i.e., longer time to forage)
149-176        TOTAL

• if you=re meeting 1^st year cygnet requirements, then you=re meeting adult molt requirements
• both adults can accomplish molt during brood rearing, therefore not overly constraining
• sometimes molt simultaneously, but not always
• molt is not constraining for swans
• optimum brood habitat = molt habitat, but unsuccessful nesters will do fine on submergents only as molting habitat

• more susceptible to hunting and lead poisoning
• more likely to fly into fences and power lines
• low flying
• not as maneuverable
• these problems can limit pioneering new wintering areas - i.e., need several years of safe migration to establish tradition (i.e., presence of good wintering habitat itself is not sufficient)

• swans spending about 35% of their time feeding
• Potamogeton & Chara important
• areas with flowing water probably more productive during winter, and will stay more ice free
• shallower water, clearer water, well oxygenated: better for plants
• probably enough winter habitat in Tri-State area for Tri-State birds - problem is all the Grand Prairie swans that also use this winter habitat-check Squires & Lockman

• building blocks of good habitat
• descriptors: size, hydrology, plant composition, plant structure
• link life history requirements to habitat

Nuphar                                      most common                most common & dominant
Potamogeton, Sparganium,        most common
& Myriophyllum
Substrate                                silt                                decomposing organic soil
[Other parameters measured bt Maj, but these are the ones that differed.]

Logan's Work - Copper River Delta
Successional                            older oxbow                   younger, ice block ponds
Plant communities                  Equisetum & Hippurus          Poa, Eleocharis
                                                  [floating, emergent mats]
Plant species diversity             more
Open water                               smaller areas

Holton's Work - Grande Prairie
Mean width of emergent
    vegetation zone                     greater
Total length of emergent
    vegetation zone                     greater
Aquatic macrophyte
    biomass                                                      no difference
        [but pairs with cygnets within an occupied area, use areas with highest aquatic macrophyte biomass]
Chara, Lemna, Potamogeton may be important foods

Lockman's Work - Tri-State
Feeding areas short
    flight from territory                 XX
More than 1 nest site
    available                                     XX
Nest material available
    adjacent to nest area                XX
Early brood feeding
    areas available                           XX
Juxtaposition/
    interspersion of
    emergent vegetation
    with feeding areas                     XX
Pair experience

See Lockman for similar list for wintering habitat
also see Squires manuscript - Wildlife 2001...for habitat characteristics.
LeMaster thesis on wintering swans in Alaska

POSSIBLE OUTPUTS
Classify wetlands into:

• Meet all requirements
• Potentially could meet requirements if management changed factor X
• Would never be used because _____________

a+b=> potential pairs supported - this approach reasonable for small wetlands, large areas like Red Rocks are harder (maybe can only refer back to historical max.)

• size (functional size - e.g., total wetland may be 100 acres but only 15 acres have conditions suitable for swan use)
• depth
• submergents 0-3g/lm2, 30% with Chara/Potamogeton/Elodea
• emergent fringe
• ice-free period - 100-120 days = management probably cannot reduce this below 100, most cygnet mortality in 1^st weeks not at end
• hydrology
• vegetation species and diversity
• spacing due territoriality

• range for hatch implies fledge is 100-120 days for Tri-State this includes good years and bad so it is not likely that habitat management can reduce this time below 100 days (even though 80 days observed elsewhere)
• is the end difference between 100 & 120 days important for Tri-State birds? --maybe not since most cygnet mortality occurs in first 2 weeks after hatching
• must reference ice-free at appropriate depths
• lack of emergent or floating-leaved vegetation in Tri-State and this forces feeding assistance behavior by adults
• most management areas have the capability to destabilize water level & create emergent vegetation
• what about dropping water levels just before brood rearing to make things like P. pectinatus more available to cygnets

• presence of water throughout ice-free period?
• depth variation among and with in years
• are water levels increasing during laying & brooding rearing?
• do you regularly see mudflats on these wetlands towards the end of the season
• (i.e., are those likely to be shallow zones)
• presence of fish, pelicans, cormorants (indicates more stable water level)
• general bathymetry - e.g., % of 10", % at 2'...
• how many years out of 10 (30?) has it been dry
• annual ASCS photos vs climate data

• when do you first see new green growth of emergent vegetation?
• when do you first see floating leaves on surface of submergent vegetation?

Many of these management factors apply to a limited number of sites (e.g., with govt management authority with water management capability)

Classification approach - each step may require answering a number of questions:

0.    % at certain depth
                    Yes --> 1.                   No --> C
1.    ice free long enough
                    Yes --> 2.                  No --> C
2.    sufficient food to put on reserves to lay
                    Yes --> 3.                   No --> B
3.    is these a nest site (e.g., floating mats, etc.)
                    Yes --> 4.                    No --> B
4.    is there sufficient food for cygnets (also enough for adult molt)
emergent vegetation or submergent vegetation at surface
                    Yes -->A             No --> B
    This process results in a problem statement.

More Details for Classification Scheme:

0.   Percent at certain depth

1.    Ice-free days

• Number of continuous ice-free days
• How many years out of 10 would you have sufficient ice-free days
• How late can ice-out occur and still meet this requiremen (related to photoperiod that drives swan nesting behavior)

• Presence of (Valisineria, Sagittaria, P. pectinatus, Scirpus) vegetation with large, below-ground resources
• If present, what % of area does this vegetation cover?
• Is leafy vegetation present (Chara/Potamogeton/Elodea) ? If not, then not good resources for swans - only P. pectinatus will supply tubers (Eleocharis and Sagittaria would not be actively growing yet)
• May need to first ask where swans are wintering and staging - are they sharing wintering/staging areas with other swans - are they foraging before they arrive at nesting area if they are sharing wintering/staging areas but there Are productivity differences then probably due to differences in resources at nest site
• Are swans feeding off-site during pre-laying period?
• History of swan use for area (e.g., # years out of last 30 they have nested here)
• How many years have clutches hatched?
• How many years have broods fledged ?

• presence of robust emergents (cattail, bulrush)
• presence of Carex, Equisetum....
• muskrat/beaver population
• interspersion (match to pictures)
• if a band of emergents, how wide
• presence of floating mats of emergent vegetation
• proximity to disturbance

• see #3
• see # 2 (herbaceous component)
• at hatch, how close to surface are submergent resources
• invert abundance and diversity
• does adult feeding assistance occur - are adults tipping up or feeding well below the surface (tells you about availability to cygnets)
• has brood been moved off nest territory
• presence of brooding sites
• increasing or decreasing water level
• presence of water through brood rearing

• Red Rocks - be there at hatch & evaluate availability of resources to brood, e.g.: Is there adult feeding assistance?  How close to surface is sago? General food habits (e.g., inverts?)
• also do this at Yellowstone (discrete wetland basins, more natural)
• fly Red Rocks for nest locations, then go on ground and see what factors may allow tighter packing (e.g., streams between territories);  also do @ Grays Lake
• look at climatic records to get an idea of hydroperiod and long term variation
• aerial photos to compare gross differences in vegetation across years (E.g., acres of emergent vegetation)