Basic Ornithology: Bird Communities

life of those who are alive one two three morning my name is Ramesh I’ve been studying birds – the last 12 years in fish and I’m going to talk to you today about the kind of work some of those themes or concepts that I started talking about communities which is how why various species of birds coexist in the same place at the same time we move on to biogeography which is the study species distributions why a species distributed in certain places what are the causes for patterns and distribution species distributions of knowledge skills geographically large geographical scales continental scales or two of the scales as for this dish so what is the bird community said we have even I think you would play different populations of birds a given area the given time that’s very close so community is a set of ecologically interacting species but interactive organisms that occur in a certain place and at a certain time so they have to be there the same place and happen at the same time and they have to internet ecologically so the interactions being you know radiation competition facilitation and we’ll talk about all those interactions but usually when you talk about communities they’re not limited to actionable groups so community could be all the trees that make up the forage for the insects that the birds eat and then the mammals that prey on the birds all of those interacting species form a community when we talk about bird community is what we are talking about is used to what about assemblages assemblages I set some species of groups of species that are found at a particular location which are usually taxonomically in the same room so you can talk about assemblages of priests and the signatures of birds but when we say community cause you said were to be entomology what we actually mean is that we’re studying bird assemblages rather than all the interactions that happen between birds and other taxonomic groups like plants or insects fruits and so now communities are complex things lot of organisms and communities and to make sense of communities one has to so simplify and create ways in which to describe these communities so one of the ways to do it is to look at species diversity now couple terms here if you look at the species richness is simply the number of species the community species issues so you can have 20 species of birds in desert nestled up that means the species richness of desert National Park is 20 yeah when we talk about species diversity you are not only taking into account the number of species you are also taking into account the abundances of those species right because all species are not equal when it comes to a plant it’s some species are more common other species are red so when you put together both the number of species as well as relative abundances of those species you get to a metric called species diversity this look at new communities here on the x-axis is something effort in us so right over there you’ve not done any something you’ve not gone out and counted Birds look for birds and as you go along this axis you spent one hour two hours three hours four hours five hours and so on looking for birds so your effort in terms of looking for birds is increasing with the excess number of species now if all species were common would you find them in a short time or a long time and the rarer the species is the longer it will take you to find that species the poor effort you need to put in to find the species so this is called a cumulation curve or a rarefaction well if you look at this community here it’s got very few species right it’s not that’s the number of species or the

y-axis has got very few species but all the species are confident because it’s taking very little time to find all the species and we know this point you’re not adding any more species there are no new species being add the fact is flattened out if there were new species being added with an effort you would see something like this until you get to a point where you’ve seen all the species and so you’re not adding any most machines and so the numbers you should remain unchanged the owners certain it’s not here there are a limited number of species if there are lots of rescues you take a lot more time to find them but beyond the point you run out of species are no more species to be found and therefore the number of species remains a plateau it up so this is a speed very common species and I’m going to look at this is what’s called the right abundance curve the x-axis is abundance red so if you took all these species have you counted the numbers of individuals of each of these species species as individual species P has six individuals PCC has two individuals then the commonest species the second most common species gets a right – so the rare species may get many high ranks so the common species here gets ranked one and as you go along the ranks you get lesser and lesser individuals of that species so the y-axis is some measure of abundance and you can see here this black line has very few species it’s talking of it 30 species so this community is more species rich than this community and what we see is in tropical systems like the Western cards values you try to have a few very common species and a large number of rare species so the community as a whole is dominated by a few very common species and long tail of rare species that are at low appearances whereas in temperate forests you’re not getting you’re not going down to very very rare species fumer species but most of them tend to be relatively common is this clear this is make sense one subspecies red what could be the reasons why species are there indivisible yes and that resource is not very about it so they have to write and we will discuss six types of reality for chicks so humid pressures on species – that might be one reason why the bird is shy so what if you have a very very common species but it’s shy so you don’t see it and you think it’s a but actually it’s not so then we get detection probability is there but yes you might think a species is rare because it’s shy and you might be very short and the separation between the sexes would reduce the chances of mating number of days the female is for time for what might be very shortly and so if you’re finding a male during your breeding season is limited and that’s the reason why so that could be because the densities of these individuals are so low that the probability of you coming across a bill then you have to be is very soon so that’s a rarity in Excel product is its

number will be less compared to other species absolutely so species might be top predators which means they occupy Halle trophic levels is everybody familiar with the concept of a protocol produces consumers consumers and what happens when you over producer up to consumer energy available at higher and higher protocol this reduces as energy reduces the capacity to support a large number of individuals also reduces so gently lower trophic level species are much more common and higher profits so here are some of the reasons white species are rare the – specialized habitat requires so it’s a species limited dependent only for attempting they might be large bony large bodied species need a lot and therefore they might have to range lost distances to find food and therefore the directing is might be very large and in a given area you can you can pack it a lot of small territories but you can’t pack it a lot of large territories and that’s what the reason why that’s what a species method right behind the true key chain so they might read it is generally higher trophic level don’t know the abundance like you said you’ve been activities or the species could be at the edge of its geographic range so generally what happens is if you look at the range of the species that your graphical range of a species they tend to be most abundant in the center of the range and as you go towards the inches of the range the abundances of these species fall so it might be rare one part of it so graphic arranged with a very common sphere and there are lots of species from which we don’t know whatever they read but you have no idea why all right let’s talk about diversity so far we’ll be talking about richness let’s talk about diversity community colleges talk about three types of diversity yes high forever speedy that on diversity and calm attackers alpha diversity is the number of species okay so here are three locations what is the aqua diversity of location location 4 so the alpha diversity of these three locations is identical they all have four species doesn’t matter what those species are the species could be different so each of these symbols represents the species yeah and the number of species in each of these locations is for diversity is one location to another how many new species are back right so when you move from here to here how many new species are so pika diverse is also what turnover when you go from one site to another site what is the turnover how many species are being replaced from the previous site and common diversity is the total number of species in the region so you have a region within which you have locations each location has an alpha diversity there are differences in what species who have across locations at differences beta diversity I finally when you put alpha and we can’t ever seem together for the whole region that’s gamma levels so how many what is the gamma-ray burst since what is the tournament what is the PETA everstik relocation one-in-three see you right so concepts of Alpha Beta Gamma this year so clear yeah so these are some terms that cultures used to describe the diversity now we get a concept that’s very very important in community ecology which is called a niche the niche is the set of abiotic and biotic factors that are required for species to occur if I attack has been it occurs in the environment temperature rainfall and so on biotic factors are things like the availability of resources so how much food is available for example so I just want to show you this graph there’s temperature on the x axis rainfall in the y axis and these

are the missions of two species ok so what can you say about the niches of these species right the species like spider head does inform this species like to try and address with this report this species is able to tolerate that this species right is that so this is the baby some of the ways in which you could describe the Miche what kind of temperature rainfall areas to these species occur so in other words the mean is the environmental conditions under which our species lives as far as the resources the species uses now the two kinds of niches classic in the rap industry is the fundamental niche and that’s the require our realizing the fundamental niche is the niche that exists in the absence of biotic interactions like competition predation and so on so it’s just the environmental conditions that are required per species to occur so what F just can they tolerate if you have a species whatever just can you tolerate what rainfall does it require these sorts of factors humidity and so so that is the ability means it can exist potentially in all those regions where temperature it’s temperature requirements are made however usually species tune in that they can’t be the reason for that is they’re limited by biotic interactions interactions being competition of radiation so you might have a species that can potentially occupy a large space but because of competition from other species it cannot exist there but it’s usually comes smaller so that is called the VD arises in the presence of competition predation and so on that you give it’s better species can give cannot expand you know which are grassland so flooded grassland in the country so it’s got a very small range it can only live in that habitat if you take it out into the city that’s it so you have generally suspicious and but you have two species that share the same resources this would be some overlap in damages right so a species that uses let’s say at least like that a species that user needs like this this species used with this party but there’s some overlap in that you should look at visual up here again on the x-axis is rainfall y axis is temperature so higher you go the hotter it gets the if you go towards the right the Rainier the water the better it gets so this species here likes hot wet places that blue species here likes cooler drier places but there is some area in which both those species overlap so there is some overlap between the issues of these species and these greatly delicious would you think they would compete more or less right so if the species are sharing the same resource this would be very high competition these species so I like the concept of the niche is what for the meat but given it is a group of species with similar dishes and classically in word community ecology that killed is defined based on your type so you have fruit people was grabbed through peoples that you fruit granules that mean seeds insectivores that we’ve insects nectar was that nectar yeah so they use similar polishing strategies and I have several types so all birds within all birds that need insects on the guild of insectivores all those are improves on the guild of food concept can be extended to other things so for example if Birds all the birds that nest in three rows from the cavity nesting so the killer concept is is very very important

when you are thinking about why certain species behave a certain way or why certain species respond to environmental change in certain ways now let’s get to interact species interactions within communities and there are wide variety of species interactions in competition predation let’s get to competition and this is interspecific competition this is competition between two species and if it was within one species because intraspecific competition we are talking about interspecific competition when one species competes with each other there are two types of competition between two species this exploitation competition which is also sometimes called scramble computation that is indicted right let’s say there’s a masala dosa and all of us want that and I’m not going to interact directly with you I’m not going to fight you for it what I’ll do is get that person eat it so I don’t interact with you at all it’s a common resource that all of us share but without interacting with you directly I reduce the amount of resources available and that’s a very common sense in in the habitat and you get some word gets there earlier some species gets there earlier that depletes the number of insects available to other birds that’s what’s one exploitation coalition because they’re exploiting the resource and reducing its other species there’s also interference competition and that’s direct that’s I will steal food from it hash you would steal food from so this is a common one that you can go on fishing and catch mission come up and the guns has them so much that the Pelican says okay boss so then they cannot coexist extinction by the other and the support for these exclusion if you look at a just you know black and white black and white weight system so that’s what’s going to check out more distribution and this example very famous example from the South Pacific is for two species of who does there’s a black widow who put that one there which occurs on these islands but on new island will you find both of them coexisting so the idea being that both these species have ten very similar ecological requirements and if you put the two together one will out-compete there’s nothing in these checkerboard pattern instead you only have one species out of the species you only have one species you also see these patterns in mountains this is not a checkerboard pattern but this is from the property line bees and this is a group words for the packages so very closely related to us and you see that in lowland rainforests we have one species as you you can put a forest it’s a replaced by one species closely related species you move up between the club forest third species comes in and completely different species so nobody boundaries between the elevational ranges of the skill this will not coexist with this there will not be found in the same is this is only here so they sharp boundaries between potentially competing species on elevation please that’s why you tend to see as you go up in elevation competition occurring at these edges and then the whole community turning over because you’ve got sex of completing species I’ll up and remote down and you simply

turn over as you go up interesting recent study that came out only last month this is about two pairs of sister species so they’re very closely related species these two are sister species which means the share a common single ancestor these two are another pair of sister species these two species do not different territories there is no territorial difference therefore is whether the like they don’t different variants these very very strong character of diligence and fight for them so what you see here this is elevation on the y-axis and these are the ranges of these species so if you look at the species that have no territorial defense the range is overlap right this is this one goes from 0 meters to about thousand six hundred meters that one goes from about 500 meters to less than 3,000 be just around the ones that defect that it is compete very strongly so below 1800 meters what species about 1800 meters right so is there any evidence that competition occurs in nature some of the things are what’s for density indication so if you have two competing species and you take out one you can’t take out one but there are national places for example on islands so the mainland you might have two species that are competing with each other or an island you might have one species disappeared and on the island we’ll find that the density of the other species increases greatly potentially because there’s nothing to compete with it people sense a teaspoon so that’s what density inflation there’s also some increment release we’ll talk about fundamentally realized cases competition causes the realized needs to become much smaller there’s a fundamental age and in the absence of competition you can expand your you should eat more things you can live in different habitats and that is because the the competitor that was limiting you to a particular habitat giving you your foods is now no longer present and therefore you expand your the third thing is something called character displacement it is wrong terms used in community ecology a captive displacement is where if you have two competing species they pertain to tigerish in the possible characteristics so if you if you and I are competing and we both are kingfishers people who live in the same place and we’re eating the same food could coexist to be able to coexist what we’ll have to do it’s just not feeding with the few things I have to prove that you have to grow a large a peak because you need new class of fish I’ll have to do a small of me because I worked a specialized once polarization but if I’m alone I can eat all so when officials are together their peaks will diverge but when there’s only one species there it does not need to specialize and therefore finally about competition how again how the species avoid interspecific competition and here is one way that you could do it in species will do it in many ways the separation they do it by between habitat segregation within a region we didn’t have that segregation or segregation in time segregation means just separation right so graphic segregation means I can’t live with you so your range is dramatically different of mine so I have an occupy this part of the range you occupy this part of the range when we move over that because we both of us cannot coexist so that’s Jo graphical simulation there’s something called mean habitat segregation which is in the same region I can occupy marshland you occupy forests so we do not compete because the habitats that you prefer and have a sport that we use are different then this we didn’t have it at segregation so all of us this is a classic example by Hudson from the 50s is the five species of Warblers that all breed and feed in coniferous trees but within the water stream which is their habitat they use different parts of the forest trees for foraging so to keep me overuse the top the

blackberry uses the top and by the bay breasted use is just the center the yellow room uses the bottom part and the black node which uses the center but it also features of older use of the pancakes so within the pine tree you have five species of gobblers but they’re all segregating within the habitat of our computation so and this aggregation for example patsy pollen somebody all right so now this competition commensalism is another kind of interaction where two species involved one species benefits from associating without with the other species but it does not affect the other species that is associated so the buffalos walk through the grass disturb insects which the kathleen benefits from but it makes no difference to falafel right so it’s a very aggressive person then they build nests around them or next to them because they know that if a predator comes in the black ground was going to attack it so their nests are also safe so they get benefits from associating with a black chrome another one is what is called mutualism mutualism is an ecological interaction in which both species pay so I bring something to the table you bring something to the table both of us benefit a good example is when a mix species bird flocks where in fact the spiders are not interested four inches in large groups not applause in the other group so they’re searching for insects in the undergrowth their head is all this stuff in believes and queens and so they can deduce the drama bonilla that feeds on flying insects so sitting looking around for insects and a flying above and if you go off and cache misses it while it’s you know it’s also looking around for reddit so the drongo is a very good what is in it but what these two is the flushing section to the air which the drongo can eat so the probe goes getting forging benefits from associating with these species and one of these species that because this is the host from the other mixed species for clocks me species bird flocks are groups of insectivorous birds that forage together so you can have a food you can have up to 40 species in the same clock or moving together or feeding together right so it’s not as if you know this species feature that species feeds them nor doing things independently it’s a very cohesive group and these groups are where species include species are responsible for bringing the group together and for maintaining those groups over time and this was the foreign interest disease which is providing some benefits to the Italian species and generally in this slope you can find the in interactions you can find competition radiation is a major factor that leads to the formation of these flocks because the more words there are the less of the transfers of any one but being predation is a very important these are like me at home and there are lots of aspects of these species clubs that are very interesting and not yet to be studied

so then if these with lots of species why do only certain species occur together why not all species so this each of these dots is a species they’re all related somehow that’s just that shows how many species are and each species differs in its traits so the sizes of these dots the colors of these dots and the patterns with you means lots of factors in that trade so sweet so the black species are all let’s say insectivores ferns that they’re in body size and so on so this is a trace but all the species can’t occur in the same that same temperature some species like the poor some species like warm warm and balanced so there’s a habitat imposes a filter so if it if your temperature range is 20 degree Celsius to 20 degree Celsius obviously something that likes my understand is not going to so that’s filtered out and something that likes giving warm temperatures that’s also filtered out so there’s a habitat that imposes a filter and then you get a habitat species where this is the most similar in their traits and finally at more local scales competition predation facilitation so again mixed notes are a very interesting system because you have a large group of species there’s a filter the filter being feeding insects so only in second verse birds can join mitzvahs X so then you’ve got this pool the local species for which then assad’s itself into various kinds of flocks so if there was interactions associated I associated you get once you get a new structure its flow if competition is driving the structure of these mixed lofts then you want to have as dissimilar species as possible this is at both open up much in their dishes so competition should lead to different species associated different kinds of species if facilitation is similar species associated there’s no competition in row then you see you should see flocks data structure that way so this again keeping in mind mix species locks are a very very interesting system in birds and your question is in community ecology for a lot of questions a very good morning systems to work we will finally take with food change the food groups every piece for every future but it’s just who eats what right so a food web is a very complex thing Jake is a single-stranded so see that’s the point you know that’s Jane and the reason why we’re talking about that is understand how communities are structure is it’s top-down processes of water these means something’s happening to the power at a higher profit level so predation is what is structuring communities so if you remove the predator the communities will change drastically bottom-up is where the availability of resources is what drives the way in which it is a structure so yes this example it’s not Birds I know but they’ve been interesting sea otters prey on what’s going to not see me and what eats kept sea urchins so yes yep now Kilauea Rishi eat seals earlier in this area in the Bering Sea for some reason seals disappeared from infection water and see these started sea otters so the top predator in this system in the kelp forest discipline very disappear sea urchins Rose gray sea so that when they work or not to sea otters there were very few sea urchins then with the Otters disappear the sea urchin numbers grazing went up and kelp which is not abundant earlier reduce greens so this is one example of a top-down regulation

but in general communities income is both bottom-up and top-down processing operate together so that amount of resources that is also water so I’ve been in here and if you have any questions you