SECURITIES AND EXCHANGE COMMISSION

Washington, DC 20549

x

Rule 13d-1(b)

o

Rule 13d-1(c)

o

Rule 13d-1(d)

1.

Names of Reporting Persons
Brookfield Investment Management Inc.

2.

Check the Appropriate Box if a Member of a Group

(a)

o

(b)

o

3.

SEC Use Only

4.

Citizenship or Place of Organization
Delaware

Number of
Shares
Beneficially
Owned by
Each
Reporting
Person With

5.

Sole Voting Power
603,900

6.

Shared Voting Power
None

7.

Sole Dispositive Power
1,470,500

8.

Shared Dispositive Power
None

9.

Aggregate Amount Beneficially Owned by Each Reporting Person
1,470,500

10.

Check if the Aggregate Amount in Row (9) Excludes Certain Shares o

11.

Percent of Class Represented by Amount in Row (9)
7.48%

12.

Type of Reporting Person
IA

Item 1.

Item 1(a)

Name of Issuer:
CoreSite Realty Corp.

Item 1(b)

Address of Issuer’s Principal Executive Offices:
1050 17th Street, Suite 800
Denver, CO 80265

Item 2.

2(a)

Name of Person Filing:
Brookfield Investment Management Inc.
AMP Capital Brookfield (US) LLC
(together, the “Reporting Person”)

2(b)

Address or Principal Business Office or, if none, Residence:
Brookfield Investment Management Inc.
Three World Financial Center
200 Vesey Street
New York, NY 10281

AMP Capital Brookfield (US) LLC
71 S. Wacker Drive, Suite 3400
Chicago, IL 60606

2(c)

Citizenship:
Brookfield Investment Management Inc. – Delaware
AMP Capital Brookfield (US) LLC – Delaware

2(d)

Title of Class of Securities:
Common stock

2(e)

CUSIP No.:

21870Q105

Item 3.

If this statement is filed pursuant to Rules 13d-1(b), or 13d-2(b) or (c), check whether the person filing is a:

a.

o

Broker or dealer registered under Section 15 of the Act;

b.

o

Bank as defined in Section 3(a)(6) of the Act;

c.

o

Insurance company as defined in Section 3(a)(19) of the Act;

d.

o

Investment company registered under Section 8 of the Investment Company Act of 1940;

e.

x

An investment adviser in accordance with Rule 13d-1(b)(1)(ii)(E);

f.

o

An employee benefit plan or endowment fund in accordance with Rule 13d-1(b)(1)(ii)(F);

g.

o

A parent holding company or control person in accordance with Rule 13d-1(b)(1)(ii)(G);

h.

o

A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);

i.

o

A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940;

j.

o

A non-U.S. institution in accordance with Rule 240.13d-1(b)(1)(ii)(J);

k.

o

Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K). If filing as a non-U.S. institution in accordance with Rule 240.13d-1(b)(1)(ii)(J), please specify the type of institution:____________________________

Item 4.

Ownership

Provide the following information regarding the aggregate number and percentage of the class of securities of the issuer identified in Item 1.

a.

Amount beneficially owned:
See the response(s) to Item 9 on the attached cover page(s).

b.

Percent of class:
See the response(s) to Item 11 on the attached cover page(s).

c.

Number of shares as to which such person has:

i.

Sole power to vote or to direct the vote:
See the response(s) to Item 5 on the attached cover page(s).

ii.

Shared power to vote or to direct the vote:
See the response(s) to Item 6 on the attached cover page(s).

iii.

Sole power to dispose or to direct the disposition of:
See the response(s) to Item 7 on the attached cover page(s).

iv.

Shared power to dispose or to direct the disposition of:
See the response(s) to Item 8 on the attached cover page(s).

Item 5.

Ownership of 5 Percent or Less of a Class.

Not applicable

Item 6.

Ownership of More than 5 Percent on Behalf of Another Person

Clients of the Reporting Person have or may have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, securities held in their accounts. No such client is known to have such right or power to more than 5% of the class of securities to which this report relates.

Item 7.

Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.

Not applicable

Item 8.

Identification and Classification of Members of the Group

Not applicable

Item 9.

Notice of Dissolution of Group

Not applicable

Item 10.

Certifications

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect.

Date: February 14, 2011

Brookfield Investment Management Inc.

By:

/s/ Seth Gelman

Name: Seth Gelman

Title: Chief Compliance Officer

AMP Capital Brookfield (US) LLC

By:

/s/ Seth Gelman

Name: Seth Gelman

Title: Chief Compliance Officer

Brookfield Investment Management Inc.

By:

/s/ Seth Gelman

Name: Seth Gelman

Title: Chief Compliance Officer

AMP Capital Brookfield (US) LLC

By:

/s/ Seth Gelman

Name: Seth Gelman

Title: Chief Compliance Officer